BRIDGE BUILDER MANUAL 2014

2014 CABLE SUSPENDED BRIDGES

FOURTH EDITION

FOREWORD Bridges to Prosperity Suspended Bridge Manual

Dear Bridge Builder, Welcome to Bridges to Prosperity’s fourth edition of the Suspended Bridge Manual! This footbridge manual has been evolving since an engineer from Switzerland, Robert Groeli and his organization, Helvetas, began to adapt traditional chain suspended footbridges built by Nepalese villagers into designs that could be replicated in rural communities around the world. Some of the first Bridges to Prosperity staff trained in Nepal with the INGO Helvetas, and have since further refined these designs to make them as locally viable, efficient and sound as possible for communities around the world. Along the way, Bridges to Prosperity has worked with local communities to build more than 160 bridges in 18 countries as of the publication date of this 2014 edition. And we hope you will join us to build another score of bridges in even more isolated rural communities! The need for increased access to basic infrastructure continues in places where people live with the least resources; the World Bank estimates that a billion people live with out access to sufficient infrastructure. At Bridges to Prosperity, we build to educate; practically this means that we prioritize training bridge builders around the world to increase the number of people who can work with communities to build safe and long-lasting river crossings. For children to get to school year round, for mothers to get to the hospital when their babies are coming, for subsistence farmers to sell their produce and be able to pay for school and doctor’s fees. We believe that access to infrastructure is a human right that every person deserves. Lofty (yet important!) ideals aside, this manual is intended to be the first step on your journey to building a footbridge with a community. We have training videos in English and Spanish available at http://vimeo.com/album/1961528 that supplement this manual series. Most importantly, we welcome collaboration and consultation with anyone using our resources. Along these lines, please follow the Terms of Use included in the manual series and email [email protected] if you are using our resources to build a footbridge. On behalf of Bridges to Prosperity, I thank you for your interest in bridge building! Please keep in touch.

Avery Louise Bang Bridge Builder and CEO Bridges to Prosperity

VISION & MISSION Bridges to Prosperity envisions a world where poverty caused by rural isolation no longer exists. Our programs provide access to healthcare, education and markets by teaching communities how to build footbridges over impassable rivers, in partnership with organizations and individuals. We prove the value of our work through a commitment to the community and its bridge that lasts long after the opening celebration. PRINCIPAL STRATEGIES We build to educate. We provide education programs that teach footbridge construction to reach the greatest number of people in need. We build to innovate. We develop, continually improve, and share engineering solutions that are safe, replicable, and locally viable. We build to inspire. We provide opportunities for leadership development and personal growth through international collaboration.

For more information about Bridges to Prosperity, visit: bridgestoprosperity.org

Certification Programs

Project Certification Bridges to Prosperity certifies bridge projects built in compliance with the organization’s standards. Project certification from B2P, the world leader in rural footbridge design and construction, demonstrates the level of quality of a given project, and links it to a growing network of more than 160 footbridges that provide crucial access for rural communities. Projects are certified as Silver, Gold, or Platinum, depending on the degree of independence from B2P direct oversight, and the proficiency of the project manager. To learn more about criteria for project certification, please visit bridgestoprosperity.org. Bridges to Prosperity encourages groups and individuals interested in project certification to get in touch at in the early stages of project planning, at [email protected].

• Comprehensive   Bridge   Construc2on   • Project   Management   • Field  Hold  Points   • Advanced  Safety  

Technical  Supervisor  

Mason  

• Basic  Bridge   Construc2on   Tasks   • Plan  Literacy   • Basic  Safety  

Construc2on  Manager  

Local Bridge Builder Certification Bridges to Prosperity is focused on building beneficiary-driven bridge construction programs internationally. To meet these goals, we have training programs for local technicians at various levels so that eventually, all bridges are entirely built through locally-led initiatives and capacity in a given country.

• Design   • Site  Supervision   • Cri2cal   Construc2on   Sign-­‐Off  

ACKNOWLEDGEMENTS 2014 Bridge Manuals

The 2014 version of this manual is possible thanks to the following organizations:

Strategic Partners

Bridge Partners

Anonymous Aall Foundation



Bridge Sponsors

Heco Slings Corporation

Program Supporters

Established Footsteps

INTRODUCTION Bridges to Prosperity provides isolated communities with access to essential health care, education and economic opportunities by building footbridges over impassable rivers. We build to educate, and this manual is a core component of our open source approach to sharing our resources and experiences. If you know of a community in need of a pedestrian bridge, or live or work in one, the first step is to gauge this interest from both citizens and local government bodies because intensive community participation is required. Volume 1 describes roles, responsibilities, and commitment from both community members and the organizing organization or individual required for a successful bridge project.

BRIDGE BUILDER MANUAL 2014

VOLUME 1

COMMUNITY DEVELOPMENT FOURTH EDITION

2014

VOLUME 1: COMMUNITY DEVELOPMENT Table of Contents Section 1: Community Participation 1.1 Importance of Community Participation

1.2

Components of Community Participation

Section 2: Roles and Responsibilities 2.1 Community Bridge Leadership - The Bridge Committee

2.2 2.3

Government Involvement Partners and Organizations

Section 3: Project Evaluation 3.1 Introduction

3.2 3.3

Anticipated Traffic Improvement to Livelihood

Section 4: Sample Proposal and Budget 4.1 Proposal Guidelines

4.2

Sample Proposal and Budget

Volume 1: Community Development

8

SECTION 1: COMMUNITY PARTICIPATION 1.1

Importance of Community Participation

B2P believes community participation is one of the primary contributing factors in successful development work, especially in rural infrastructure projects like a footbridge. The community is the bridge owner and user, both benefiting from the bridge and attending to long-term bridge maintenance and repair. For these reasons, community participation is key to B2P footbridge planning. Needs-based demand: it is the responsibility of the community to express their need for a pedestrian bridge. They can express this need to the local authorities, to the regional or national government, to non-profit organizations working locally, or directly to B2P. The community will be expected to participate in the bridge construction and, once finished, the bridge will their responsibility, so it is essential that the expression of need come directly from the beneficiary.

1.2

Components of Community Participation

While the local climate sets the expectations for the level of community participation in a project like the construction of a bridge, B2P generally works on the premise that unskilled labor and the provision of local materials will be a community responsibility. In some places, it is expected that this will be provided on a volunteer basis while in other locations, where poverty levels are extreme and/or a history of many international aid projects have made volunteering unusual, labor and/or materials will be paid at local rates, preferably by the local government. Community Participation includes: • Transporting materials from the main road to the bridge site • Collecting locally available materials including sand, gravel, stones and wood • Site clearing and excavation • Loading and unloading materials that are delivered

Volume 1: Community Development

9

SECTION 2: ROLES AND RESPONSIBILITIES 2.1

Bridge Committee

Community participation begins with key members of the community taking a leadership role in the coordination of the project, from site preparation, to material collection and construction, and ongoing maintenance upon completion. B2P refers to this group of leaders as “The Bridge Committee.” They are often community leaders, school teachers, elders and other respected community members serving in the role of project coordination. Bridge Committee members are expected to attend all meetings with partners to voice interests and share in decision making. The Bridge Committee must work together, function as a body and acknowledge their duties as representatives of their community. The Bridge Committee should not make decisions, particularly financial commitments, on behalf of their community without the endorsement of the community. For example, if the Bridge Committee is requested to provide meals and accommodation for masons, or facilitate the collection of additional materials, the Bridge Committee must first consult the community before agreeing to any commitments that affect the community at large. Once bridge construction is complete, the Bridge Committee is given a basic Maintenance Manual to ensure that the upkeep and standard of safety of the bridge are upheld for the lifespan of the bridge. A more complete maintenance checklist should be left with the local municipality engineering office.

2.2

Government Involvement

Local government offices and officials will likely play a significant role in the preparation and implementation of the bridge. Their support can provide substantial assistance: officially, with government required documentation and approvals for use of land; logistically, with the provision of vehicles for material transportation; and regularly with financial support for construction materials and local skilled masons. Additionally, there are often existing sub-committees within the local administration, which are dedicated to the execution of infrastructure projects. Regardless of the level of commitment of the local administration, they must be involved, assuming their roles and responsibility hand-in-hand with the Bridge Committee.

2.3

Partners and Organizations

Strong partnerships can contribute to the success of a project through financial assistance, community mobilization, and technical advice. B2P partners have the ability to maintain institutional memory of the technology, and once trained on a bridge they may help other communities with bridge construction in the future. Partners can include other non-government organizations, local institutions such as engineering societies, and universities. If working in a B2P program country, consult with the B2P country program manager, or request information from B2P, as we have an extensive global network of partners.

Volume 1: Community Development

10

SECTION 3: Project Evaluation 3.1 Introduction When a community is considering an infrastructure project, specifically a pedestrian bridge, the expected benefit should be evaluated at the onset of project planning, and again after the project is complete: How many people will the bridge benefit? The number of communities, in addition to the number of individual families and businesses that will be served by the project should be determined via a traffic count at the typical crossing point. What are the benefits of building a bridge in that location? The proximity of markets, schools, healthcare facilities, and larger towns or cities should all be determined, as well as the current route people use to reach these. Evaluating these factors before and after project completion, in addition to the the level of community and outside support, helps to determine the overall benefits of the bridge project.

3.2

Anticipated Traffic

One of the most important factors in measuring the impact of a bridge is determining how many people, or how much traffic, the bridge will facilitate. Determine how many families are located on each side of the bridge and what the reasons for crossing are. How often do families need to cross? What types of facilities are on each side? Are there other crossing points up or down stream that are not available during rainy or high water seasons? If so, will bridge traffic increase during rainy season or when other crossings become unavailable? The more people a single bridge can positively effect, the more viable the project, athough traffic alone does not determine the importance of a bridge. The Bridge Committee should help facilitate preliminary bridge traffic data collection and include this information in any project proposal. Local government offices may also be good sources of data, in addition to other NGOs working in the area.

The most important factor in measuring the impact of a bridge project is determing if and how people’s lives will be improved. Determine the current method for crossing: what is the distance to and from the communities? Is it safe?, Is it accesable all year? Also, what types of facilities will become accesible once the bridge is in place that were not availble before? Schools, healthcare facilities, markets, other towns or cities, possible jobs? Will the bridge bring more traffic into the surrounding communities? If so, will there be trade or economic benefits from the increased traffic?

Volume 1: Community Development

11

3.3

Improvement to Livelihood

A very important factor in evaluating bridge impact is determing the ways in which community members’ access to essential lifelines and opportunities will be improved by having a safe river crossing. • With the current method for crossing, what is the distance to and from the communities? Is it safe and accessible all year? • Are there any types of facilities that will be accessible once the footbridge is in place that are not currently accessible? Most commonly, these will include schools, healthcare facilities, markets, other towns or cities, and possibly jobs. • Will the bridge bring more traffic into the surrounding communities? If so, will there be trade or economic benefits from the increased traffic? Could there be negative effects from increased traffic into the community? The Bridge Committee should help gather preliminary community improvement data and include this information in any project proposal. See Volume 2 for technical and social survey martials.

“Two years after the repair of the Sebara Dildiy bridge in Ethiopia, we found that the community, particularly in Gonder, had increased sale of their products by three times. Now they are able to sell their grain across the river in Gojjam for more than they previously could in Gonder and with the profits buy coffee to sell in Gonder.” Comminuty Member Gondar, Ethiopia

Volume 1: Community Development

12

SECTION 4: SAMPLE PROPOSAL AND BUDGET 4.1

Proposal Guidelines

Bridges to Prosperity recommends that you complete a project proposal to assist with securing B2P support and external funding for your project. The following outlines the suggested content, followed by an example proposal. Please adapt these guidelines to fit your needs and funder requirements.

• Photograph: When available, introduce the project with photograph that clearly illustrate the issue(s) described in the proposal. Visual aids help donors understand the need.

• Introduction: This should include the main obstacles faced by the community, as related to lack of access due to a river.

• Who you are: It is important for the donor to learn about the applicant. Inform the donor of the projects you have successfully completed in the past, the partners with whom you have worked (NGOs, government departments, i.e. Transport Department), and the positive outcomes of the completed projects.

• Describe your project: What purpose will a pedestrian bridge serve for the community? Include why your idea is economically feasible.

• The area and the people: Describe the area in which the project is planned. Providing detail about

the beneficiary population and the projected number of direct users is important. Also document the indirect beneficiary population, including anyone that may benefit from the increased traffic from the bridge. Describe the economic benefits, including types of increased income generation from the project and/or improved access to health care facilities, markets and educational and job opportunities.

• Community participation: Describe why the project is so vital to the beneficiary community and detail

what they are willing to contribute in time and/or money to see the project to completion. A statement that the community has already raised enough money to cover all skilled and unskilled labor and is willing to acquire all the locally available materials will drastically improve the project’s chances of being funded. Donors need to know that this is a project for the community, and that the community is willing to contribute to the effort.

• Specific request: Detail exactly what is needed and emphasize the return on investment. Donors like to know

that a large amount is going to be gained for their relatively low contribution. Make it clear that the project is financially viable because. For example, “over the next ten years, an esimated 10,000 students will be able to reach higher education.”

• The bottom line: “We need an investment of only [$] to complete the bridge project,” and “This bridge will improve the lives of [number] of people.”

• Budget: Include a detailed budget of anticipated costs. Following the completion of the project, submit a

report of actual expenses, including receipts. This will give the donor confidence in investing in you in the future. The following page includes an example budget for a 60m suspended bridge. Please work with a B2P representative to determine a realistic budget your proposed bridge.

Volume 1: Community Development

13

4.2

SAMPLE PROPOSAL AND BUDGET

Suspended Pedestrian Trail Bridge Project Proposal Naupachaca, Cahuac District, Yarowilca, Huanuco Peru

[Picture w/ people]

Introduction Bridges increase access for those isolated from markets, schools, health facilities, local administrative and relief services. With the addition of pedestrian trail bridges in rural infrastructure, poverty can be reduced and education and health levels improved. Approximately 30% of Peru’s population live away from vehicle roads, traveling by foot on narrow trails, which often cross rivers - small and large. The geographic region between the Andes mountains and the Amazon rainforest is one of the most inaccessible regions in the country. Combined with low population density and the inherent difficulties of building infrastructure in such terrain, there are immense challenges to community development and well being. Five years ago, over five villages were affected by the loss of a bridge to high floods. Through the Alcalde of Cahuac, those people have requested a bridge so that difficult travel is no longer a challenge to development.

Bridges to Prosperity (Implementing Agency) Bridges to Prosperity (B2P) is a non-profit organization based in the United States with operations in Africa, South and Central America, and Asia. B2P began operations in 2002 with two staff members being trained with Helvetas Nepal in the pedestrian trail bridge program. B2P brought the suspended bridge technology first to Ethiopia, and then to more than 160 communities in 18 countries. B2P’s primary focus is the transfer of technology. Bridges to Prosperity is an implementing organization. Once a bridge site has been selected for construction, B2P provides site assessment and survey, social organizational support (community mobilization), a professionally engineered bridge design, and construction management and practical training throughout the bridge construction. Bridges to Prosperity’s community-based bridge building program requires a minimum contribution from the beneficiary communities, consisting of local materials (sand, gravel, and stone) and unskilled labor. Bridge sites are selected according to community location and need. A bridge sponsor is required for the purchase of cable, cement, decking and logistical assistance. B2P believes in strengthening the local government in their commitment to the community and assisting in allocating donors, but B2P does not provide direct funding. The suspended pedestrian bridge is a low-cost alternative to the pedestrian bridges currently being constructed in Peru. In order for this transfer of technology to happen, several steps must be taken: educational training sessions and shortspan demonstration bridge training followed by full bridge construction training sites. Once an engineer or other trainee has completed the initial training course, they are invited to participate in full-construction training. The trainees and/or organizations that complete both phases of the training will be considered by B2P for future partnership bridges. These partnership bridges are led by the trainee(s) with support of B2P staff. If the secondary bridge is successful and the trainees or trained organization are interested in partnerships, B2P will consider their support for further bridges.

The Bridge After thirty years building bridges in Nepal, Helvetas has fine-tuned its suspended bridge design so that it is now internationally recognized. The suspended bridge is ideal for rural areas: construction does not require heavy machinery, but can be completed entirely by human effort. It is a cost-effective structure that requires very little maintenance, with a lifespan of up to 30 years.

Naupachaca, Cahuac, Peru The Marañon river separates five towns, with the municipal centre at Cahuac, from the provincial capital of Chavinillo. The loss of the bridge more than five years ago means that the walking time for villagers to the clinic, school, market, etc., has more than tripled for some, at least doubled for many. This means at least a two-hour walk, when once it was only half an hour. Huanuco is considered by the United Nations Development Programme as one of the poorest areas in the country. The majority of the beneficiaries at Naupachaca are living at or below the poverty line, and the number of surrounding beneficiaries is estimated as high as 10,000, with 5,000 being direct beneficiaries.

The District of Cahuac has an engineer willing to manage the project under Bridges to Prosperity’s supervision with the intention that he replicate the technology in the future for other locations requiring a low-cost solution, thus working towards the goal of sustainability. The Alcalde of Cahuac (also the treasurer of the Association of Municipalities of Peru) feels confident that he can pull together a further 20% of the total cost in cash from the beneficiary villages. The Rotary Club of Lince is willing to assist with the supervision and logistical support costs. All we need now is the remaining 60% of the cost of materials to accomplish this very important project for the people of Cahuac and its surrounding communities. A bridge survey has been completed by a local contracting company at the expense of the District of Cahuac. This survey was conducted with the traditional suspension bridge in mind and has estimated a budget of $205,000 soles ($62,121 dollars or $2824dlls/m) for a 22m bridge.

A pedestrian bridge for safe crossing over the Marañon can become a reality for a total budget of $25,000.

Please contact JaneDoe +1 555-555-5555 [email protected]



Example Budget

Suspended Bridge Direct Costs Item

Unit

Required

Price

Totals

Cable 26mm

m

391.04

9.00

3519.36

Clamps 26mm

piece

64.00

3.50

224.00

Cable and clamps

Estimated Sub-total for Cable

$3,743.36

Construction Materials Cement

bags of 40kg

200.00

9.00

1800.00

Concrete Blocks = 40 x 20 x 15 (cm)

unit

180.00

0.50

90.00

Rebar 10mm (3/8")

(9m)

6.00

5.50

33.00

Rebar 16mm (5/8")

(9m)

11.00

10.72

117.92

Rebar 20mm (3/4")

(9m)

4.00

15.00

60.00

Handrail saddles

unit

4.00

25.00

100.00

Walkway saddles - 2 cable

unit

4.00

25.00

100.00

Tying wire

kg

10.00

1.00

10.00

Plastic suction tube 3"

mts

20.00

1.00

20.00

gal

8.00

20.00

160.00

Roofing Tar

Estimated Sub-total for Construction Materials

$2,490.92

Deck Wood crossbeams - (10cm x 20cm) x 140cm

piece

62.00

7.00

434.00

Wood platform - (5cm x 20cm) x 200cm

piece

155.00

4.00

620.00

Screw - 8mm x 10cm(nailing panel to crossbeam)

unit

62.00

1.00

62.00

Deck Screws - 4" x 6/deck

unit

180.00

1.00

180.00

Smooth iron bar 10mm (3/8") (suspenders)

(9m)

32.00

7.00

224.00

Anti-rust paint (suspenders)

0.5gal

0.50

10.00

5.00

Safety fencing = 1.5m in height

mts

76.00

4.00

304.00

Tying wire

kg

20.00

1.00

20.00

Estimated Sub-total for Decking

$1,849.00

Local Materials (if not donated) Sand

m³

40.00

20.00

800.00

Gravel

m³

10.00

40.00

400.00

River rock

m³

80.00

12.00

960.00

Dressed Stone

m³

40.00

20.00

800.00

Estimated Sub-total for Local Materials

$2,960.00

Transportation Transportation of materials

per trip

2.00

100.00

Estimated Sub-total for Transport

200.00 $200.00

Labor and Technical Support Mason

daily

180.00

10.00

Estimated Sub-total for Labor Total Contingency 10% Direct Costs Total with 10% Contingency

NOTE: add costs of engineering, supervision personal, transportation and admin when appropriated

1800.00 $1,800.00 $13,043.28 $1,304.33 $14,347.61

BRIDGE BUILDER MANUAL 2014

VOLUME 2

FEASIBILITY & TOPOGRAPHIC SURVEY FOURTH EDITION

2014

VOLUME 2: FEASIBILITY STUDY & TECHNICAL SURVEY Introduction Pedestrian bridges provide isolated communities with access to essential health care, education and economic opportunities by building footbridges over impassable rivers. Bridges to Prosperity builds to educate, and this manual is a core component of our open source technical resources for building footbridges. As you continue to develop a footbridge project, Volume 2 should be used to evaluate the social and technical feasibility of the project, providing guidance in identifying key design components. Please use these manuals in coordination with other tools, resources, videos and personal support from Bridges to Prosperity, all available online at bridgestoprosperity.org in the Resources section.

VOLUME 2: FEASIBILITY STUDY & TECHNICAL SURVEY Table of Contents Section 1: Social Considerations of Site Selection

1.1 Overview 1.2 Stakeholder Participation 1.3 Socio-economic Needs Study 1.4 Bridge Committee 1.5 Site information 1.6 Preliminary Technical Assessment

Continue to Sections 2 through 6 if the site is determined to be socially and technically feasible.



Section 2: Technical Feasibility Study

2.1 2.2 2.3 2.4 2.5

Survey Material List Location of Bridge Site Topographic Survey Soil and Rock Identification Local Material Logistics

Section 3: Selection of Bridge Design

3.1 3.2 3.3

Introduction to Bridge Technologies Suspended-Cable Pedestrian Bridge Suspension-Cable Pedestrian Bridge

Section 4: Other Structures



4.1 Wind Guys 4.2 Drainage 4.3 Retaining Structures 4.4 River Bank Protection

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

SECTION 1: SOCIAL CONSIDERATIONS OF SITE SELECTION 1.1

OVERVIEW



Bridges to Prosperity uses the following chart when considering a bridge request.

Social Feasibility Assessment Community is unwilling Erosion Issues Try to locate another site nearby or work towards preventing erosion in order to consider the site in the future. Terrain Issues If bridge site location is in a flood plain or very short span, the suspended bridge is unsuitable. The bridge request should consider a suspension design or seek contractors/service providers who have the relevant experience for the site. Social requirements not met If the community is unhappy with a suspended pedestrian bridge, or requires a vehicular bridge, then seek contractors/service providers who have the relevant experience for the site.

Community is willing

Bridge site rejected

Site Technical Assessment • Topography, terrain & span • Evaluate potential for erosion • Potential placement above high flood level • Insure sand, gravel and stone available

No

Favorable

Financial support available?

Yes Secure funding from local administration, donors or reapply when funding is available

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

Unfavorable

Bridge request will be considered for the following bridge building season Future site selection process Sites will be selected, surveyed and designed based on the preceding criteria. Should several sites be available, sites will be selected by the possibility to leverage for training.



4

Steps to Project Implementation Submit bridge application form or speak with an in-country representative

1. Complete the Pedestrian Bridge Application Form, Section 1.3 of this Volume. 2. Submit the form directly to B2P either in person or via the B2P Bridge Portal (an online submission forum) or through the local government, donor and/or implementing agency . 3. At this point the project will be considered, pending a site assessment of the contributing technical and social factors.

Site assessment will determine the feasibility of bridge site. If the site is deemed feasible:

4. Ensure community participation in the project. 5. Ensure local governmental support and (as applicable) financial commitment and sign Collaboration Agreement. 6. A design, quantity and cost estimates will be prepared by B2P or other trained professionals. 7. Quantity estimates can then be utilized to secure and budget the appropriate amount of funds for bridge construction.

Once funding has been secured: 8. Consult B2P to schedule bridge construction. Scheduling may vary according to demand on B2P capacity at the time. Note: B2P is not a funding organization, however, B2P can donate cable should the community display willingness and motivation to participate in the construction of the bridge.



Complete Technical Survey, Design and Construction Schedule

10. Submit survey and design via the B2P Bridge Portal. 11. Receive TAB approval. 12. Prepare a construction schedule. Project preparation and bridge construction typically takes no more than four months from start to finish.

View Construction Videos / Attend B2P Construction Training Seminar Build Project and Track Quality Control

13. Follow the Construction Checklist. 14. Ensure Quality Control Construction photos are taken during each critical phase.

Submit Project Completion Documentation

13. Quality Control check-lists and photographs 14. As-Built drawings

Project Certification VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



5

1.2

STAKEHOLDER PARTICIPATION As discussed in Volume 1, the commitment and participation of the local community is a strong indicator of the need of the bridge. B2P only works in areas where the community demonstrates a willingness to contribute to the project. We also recommend involving the local government in early discussions of potential bridge projects. When visiting a potential beneficiary community, a meeting should be held to identify the stakeholders and their respective roles and expected contributions. The product of this meeting, or series of meetings, should be a clearly defined plan for the project and a signed tripartite agreement.

Define Roles and Contributions B2P Certified Platinum Project* example: *Program projects are also considered Platinum Projects for in-country user identification of project level. Roles Community

Organization of community work groups

Local Government

Assist community

Partners & B2P Certified Local Builders

Technical and Construction Oversight

B2P

Support and Supervision

Contribution

• • • • • • • • • • • • •

Collection of local materials (sand and stone) Site preparation Materials storage Unskilled labor throughout bridge construction Accommodations and food for mason, supervisors and volunteers Basic bridge maintenance and upkeep Skilled labor Local material as needed (sand and gravel) Purchased materials (cement, rebar, wood etc.) Transportation of materials from nearest town Construction oversight Tools and safety equipment Logistical support

• Technical support • Design and quality control approval • Cable grant



VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



6

The following forms are prototypes of a new system Bridges to Prosperity is preparing to launch, through the B2P Bridge Portal, to be found at bridgestoprosperity.org.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



7

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



8

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



9

1.4 BRIDGE COMMITTEE As indicated in Volume I, the Bridge Committee is formed by a group a community leaders and motivated individuals to ensure the community’s interests and needs are addressed and that the commitments are followed through. Ideally, this committee aligns with the priorities of existing community leadership initiatives.

.

The Bridge Committee is responsible for local bridge-building decisions, including the collection and account-keeping of necessary funds for workforce or maintenance; mobilizing the workforce; and keeping to a reasonable schedule.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



10

1.5

SITE INFORMATION The following considerations should be taken while visiting a possible site. Most of this information should be documented in the Technical Survey forms, including the notes section.

Traditional Crossing Point

The bridge site should be selected at or near an existing crossing point. For smaller rivers the bridge site should placed as close as possible to this existing crossing point. For larger rivers a detour of up to 500 m may be acceptable.

Estimate Bridge Span (L)

The bridge span for the types of bridges described in this manual is limited to 120m for suspended bridges and 84m for suspension bridges. Measure the tentative span and ensure that it is within the limits of the standard designs in this manual.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

High Water Level (HWL)

This is the absolute highest point noted by the community, including such cases as a hurricane or other large flood events. Also take note of any evidence of high water near the site, including lack of vegetation and/or erosion, and compare that with what the community indicates as the high water level (HWL). Discuss any discrepancies with the community.

Approximate height differential (∆H)

It is important to gain a relative understanding of the elevation difference between the two proposed tower locations. The final design dictates that the height difference between the towers is not more than four (4) percent of the span, but up to three (3) meters of additional tiers may be added to equalize differential. For the preliminary survey, note if the height differential is significant.

Water Table

Make note if the anchor will be submerged or not.



11

Verify Land Ownership Requirements

Land ownership is an extremely important aspect of site selection. The land owner must understand clearly what portion of their land will be used either for the bridge or for the access to the bridge. The owner must be willing to donate the land or be paid a fair price by the local government or the community. The land ownership title must be in writing, approving the construction of the bridge on the land before proceeding. In many areas, land owners will greatly benefit from a bridge being located on or near their property, relative to market and access opportunities.

Verify Sufficient Area Available for Excavation

Sufficient area should be avaliable in front of and behind tower locations to allow for the towers to be positioned. This includes three (3) meters in front of the tower and approximately ten (10) meters in the back depending on soil conditions. Rock conditions may require significantly less excavation area, but may present further excavation challenges.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



12

1.6

PRELIMINARY TECHNICAL ASSESSMENT Hydrologic Considerations When identifying potential bridge crossing points, avoid placing the bridge close to river bends or inlets .

,

Avoid crossings in which the river meanders. Often gravel-filled valleys are the residual of rivers meandering back and forth. Depending on the size of the boulders, one may establish the relative velocity of the water and determine if spanning the entire river way is necessary.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



13

Geotechnical Conditions to Consider and Avoid: Rock and Soil

Conditions to avoid with soil slopes Landslides

Rockfalls

Erosion and Seepage

Inclined Trees

Parallel or Vertical Bending Planes

Avoid

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

Avoid

Landslides

Okay



14

COLLABORATION AGREEMENT • Need and Commitment

• Local material collection

• Expectations

• Timeline

This is an example agreement that briefly outlines some of the key components of a complete agreement. The agreement should be signed by the beneficiary community or communities, the local government, and the implementing agency. The agreement should include the following:

Community • The community will elect a Bridge Committee to oversee the cooperation of its members, be the liaison with the implementing agency, and be in charge of long-term maintenance (typically a minimum of three members, and preferably including women).

• The bridge built under this agreement will be owned by the entire community whose efforts were invested. Ownership shall not rest with the property owner who

owns the underlying property. To ensure understanding, the property owner must sign a property release declaration prior to the commencement of construction. This is the sole responsibility of the community to evaluate and resolve.

• Community members chosen for labor will be chosen fairly and shall not be required to provide more labor than others. Value shall be given to each person who

contributes their time. The value of work should be specified as the community contribution. The Bridge Committee will record each community member’s time contribution.

• The community will collect all local materials as available (quantities should be specified), provide a workforce to construct the bridge (specify number of workers needed per day), and work under the construction quality standards as designated by construction manager and provided throughout bridge construction.

• The community promises to care for all materials and tools provided, and prevent them from damage and theft. • The community will host and feed the Mason and Foreman throughout the construction as well as the implementing agency supervisor when needed. If a volunteer group is coming to work on the bridge, specify the role of the community in hosting the group (accommodations, cooking, etc.)

• Upon completion of the bridge, the Bridge Committee will be responsible for ensuring the continued upkeep and safety of the bridge according to the instructions

provided. The bridge is a community asset and shall be treated as such, with the entire community contributing to bridge maintenance. These tasks will be agreed upon by the Bridge Committee on behalf of the community.

• The community acknowledges the requirement of participation in order for this project to be completed.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



15

Local Government

• The local government is committed to the project and will support both the community and the implementing agency in their effort to build the bridge. It will appoint

a contact person (preferably a local engineer) to work with the implementing agency and the community to ensure community participation and that all local government commitments are met.

• The list below includes everything that should be asked of the local government. However, often only some of the items on this list are provided. B2P recommends insisting on a minimum of local materials and transportation. Specify exact quantities and value per local government estimates.

• Sand and gravel when not available locally • Construction materials. • Transportation of all materials • An engineer to work with the implementing agency to be trained on our bridge building methods • Machinery, if available (excavator, cement mixer, jack hammers, etc.) • Other materials as available (wood, cement, rebar, etc.)

Implementing Agency • The Implementing Agency will survey the site, design the bridge, and supervise project implementation per high quality and safety standards, and in the time specified, given all other parties to the agreement cooperate fully.

• The Implementing agency will pay the salary of one (1) mason/foreman to be on site daily, manage the work and coordinate with all other parties. • If a volunteer group is coming to work on the project, specify the details. • The Implementing Agency will supply the following materials for the bridge: [Specify all materials and their value.] • The Implementing Agency will provide the cables and clamps needed for the bridge. The quality of those are essential to the bridge safety and duration and are

brought from the US to ensure their quality. Specify quantity of cable and clamps with their estimated value. Those values are not the cost, but the value of the material in-country, mainly based on shipping costs. (Usually $10-17 per clamp, $5-10 per 1-meter of donated cable)

The agreement should include a total estimated cost of the project, including community volunteer work, local materials value, design and supervision value (usually ~25% of direct costs), etc. It should then specify each party’s contribution in percentage. The agreement should also include estimated project start and end dates.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



16

SECTION 2: TOPOGRAPHIC SURVEY 2.1

SURVEY MATERIAL LIST

Materials Required for Survey (using either an Abney or an automatic level):

• Maps with tentative location of the bridge and any available background information • The following items will be necessary when performing either an Abney level or an automatic level survey:

• Plum bob • Camera • Pick • Shovel • Notebook and pencil • Measuring tape: 100 m • Fluorescent spray paint • Range finder (optional) • Calculator with sine and cosine functions • Measuring tape: 5m • Hammer • Survey sticks

• If performing the survey with an automatic Level, you will also need a tripod and graduated level rod.

2.2

LOCATION OF THE BRIDGE SITE

• Describe the location of the bridge site. • Draw a bridge site location map covering the proposed bridge’s area of influence, as shown in the example on the next page. The map should contain the following information: • River system with names and river flow direction • Location of proposed bridge and traditional crossing point • Location of the nearest bridge • Existing trail system and, if required, specify length of new trail for access to the proposed bridge • Location of the villages, health clinics, schools and other important places with approximate distances to the bridge site

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



17

Chart Bridge Location

*See technical survey form at end of section.

Map Example:

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



18

2.3

TOPOGRAPHIC SURVEY The following section outlines the steps required to complete an Abney level site survey including in-depth descriptions of each step and an opportunity to complete your own survey. B2P strongly recommends reviewing this section as well as the standard drawings and watching training video #3: Site Survey before heading into the field. Training videos can be found under Resources on www.BridgestoProsperity.org

Survey Area

A profile along the proposed bridge centerline is recommended to be a distance of at least 30 meters behind the proposed tower locations. In some cases, the tower locations will need to be moved due to design parameters. A more inclusive survey will provide more options; the more information, the better. This section includes instructions on how to survey and draw a cross-section of the river along the centerline, a representation of the river, the river side-slopes, and abutment/foundation/ anchor placement(s). If the proposed bridge span is greater than 120 meters for a suspended design or 84 meters for a suspension design, it is outside the scope of this manual. If there is a professional engineer working on the design, further survey information may be needed to include both up and down stream topography as well. Consult the design engineer before completing the field survey to ensure proper information is gathered.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



19

Abney Level Survey - Overview Set the Bridge Center Line Find an area for a crossing that meets all previously mentioned criteria. Fix the bridge center line with two permanent benchmark points: A on the left bank and B on the right bank. Permanent benchmarks A and B should be fixed on rock outcropping along the bridge center line if available. If a rock outcrop is not available, these points should be marked on trees or boulders sufficiently embedded into the ground so as not to shift or move. Note: Left and Right are in reference to your position when facing downstream. It is important to remain consistent with directions. Sketch the Profile Draw a rough sketch of the profile or cross section of the bridge axis with benchmarks A and B, with all the survey points and topographic features including tentative position of the bridge foundations, current water level and highest recalled flood level (HWL). Select Station Points Estimate the most feasible locations for the towers on each side of the river (Left and Right). One of these points should be the primary survey station. Mark Survey Points Additional survey points along the center line should be fixed to survey the bridge axis profile as shown in the sketch in the survey setup section. These survey points should be fixed at breaking points of slope and terraces, which will accurately indicate the topography of the bridge axis. The profile should cover up to 30m behind the proposed main anchorage block up to the edge of the river flow.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



20

Short Span Trail Bridge Standard

Suspended Type

Step by Step: Reading the Abney Level

Reading an Abney Level

2.5.3 SURVEY METHODS

The purpose of the Abney level is to find the angle between the point of the viewer and the point of 1. Look into the viewfinder (the end that is There are two optionsand for conducting the topographic non-extendable), adjust the end of survey. D interest. The Abney can be used for both the initial survey and setting the cable sag. bridge,the a profile along the bridge axis or a more detailed includin viewer until the point of interest issurvey in In general Windguy Arrangement is not required for bridges with span u focus. 2. angle • Unlock A detailedthe profile alongprotractor the selectedknob bridge by axis is suffic unscrewing it slightly. arrangement. A topographic profile can be made by the Abney le 3. On the Instrument left side of the viewer, a level bubble a Level is necessary. should be visible. Adjust knob until bubble in viewfinder. • is Forcentered bridges requiring a windguy arrangement a more detailed to 4. Tighten the knob. which a detailed contour plan can be plotted. This type of survey 5. Record the number of degrees and minutes the point (seeLexample). 2.5.4 for SURVEY BY ABNEY EVEL 6. Note if angle is positive or isnegative. The main function of the Abney Level to measure the vertic Pointing thetheAbney causestape, the ho distance d between survey level points downhill with a measuring the knob to swing away from the user and difference of elevation ΔH can be calculated. is thus negative (see example).

Measurement of Vertical Angle: The principal of measuring the vertical angle by the Abney L procedure described below: Chapter 2: Survey and Bridge Site Selection

Topographic Survey with Abney Level

27

The measured distance between two points and the angle found with the Abney level gives all of the necessary information to calculate the vertical and horizontal differences between the two points. Using the law of sines, a theoretical triangle may be created between the shooting point, A, and the point of interest, C (see diagram to the right).

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



21

Survey Setup • • • •

Use two sticks of equal height. Approximately 1.0 meter in height is convenient. One person with the Abney level set on top of one stick should be fixed at the survey station. A second person will move from point to point with the second stick. A bright colored tape or string helps for viewing the point of interest (top of the second stick). While surveying, make sure the surveying sticks are vertical. For the first stick, the Abney level will have to adjust in angle while the stick remains vertical.

Step by Step Abney Level Survey Procedure • Set centerline. Mark points on rock or ground on either side with spray paint • Sketch a profile of the crossing along the centerline. • Mark survey points along the contour of the land: points that increase or increase or decrease more than 1.0 meter(s) in elevation should be included. Name these points a, b, c, etc. Include the existing water level and the high water level representative of flash flood or hurricane conditions. • The final survey will connect the survey points with straight lines so be sure you have enough points to accuratley plot the crossection.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

• Select 2 points for tentative survey station locations L and R. • Measure the distance between survey station and survey point “a” with measuring tape and document each point. • Before moving, measure the angle between survey station and survey point “a” with Abney level and document. • Continue until all survey points have been documented. • Note any additional information including trees, large rocks or other immovable objects.



22

Automatic Level Survey - Overview It is important to check your automatic level to ensure that it is functioning properly. This can be done using the two peg test, which is explained later in this section (page 27). The following steps and procedures must be followed when surveying bridge sites with an automatic level.

Survey Procedure: • • • •

Sketch the profile Establish horizontal control and bridge center line Establish vertical control How to determine bridge profile elevations: • Perform two peg test • Correct level setup • Read a level rod • Run a level circuit and establish elevations • Move the level • Set and level benchmarks

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



23

Sketch the Profile Draw a sketch of the profile or cross section of the bridge axis with axis points R (right tower location) and L (left tower location), with all the survey points and topographic features, including tentative position of the bridge anchors, low water level and highest recalled flood level.

Establish Horizontal Control and Bridge Center Line Set the level on your assumed centerline Tower side A. Have a person with a plum bob set points on Tower side L. Sight through Tower L’s desired location and set points along the alignment. At least three points should be set beyond the tower, preferably at the tower, between the tower and anchor, and beyond the anchor (the last point located approximately 30m beyond the edge of river flow). Set additional points as necessary to accurately show the topography along the bridge center line. Again, the final profile will connect the points surveyed with straight lines, so make sure there are enough points. Turn the level 180o to establish similar points on Tower R side along the bridge axis. Finally, use a tape measure or digital distance finder to measure between the points and mark all points and distances on the bridge profile.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



24

Establish Vertical Control Find a secure location on each side of the bridge and set points or bench marks (BM#1 & BM#2) to use as your vertical control. These points DO NOT have to be on your bridge centerline. Assume a generic elevation for BM#1 of 100.00m. Finally, run a level circuit (shown on page 24) through the two points to establish the elevation of BM#2.

Determine Bridge Profile Elevations Finally, run a level circuit (shown on page 32) through all of your points to determine elevations and the overall profile of the bridge.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



25

How to Perform a Two Peg Test The two peg test is performed to determine the amount of error and eliminate it from the survey.

The following steps should be followed when performing the test:

S2

S1

1. Set two points in line 40m apart. 2. Set the level centered between the two points. 3. Take a reading of both points A and B, S2 and S1 respectively. 4. Have the rodman stay at point B and pick up the level and move within 5m of the point while

A

remaining in line (note this point is NOT in between points A and B).

L/2

B

L/2

5. Take a reading at point B, then at point A, S3 and S4 respectively. 40m

6. Using the error equation to the right, the absolute value of ‘e’ should be less than or equal

S3

S4

to 3 cm. If the value of ‘e’ is outside this threshold then you should redo the exercise. If your measurements still do not check out, you will need to take the level to someone who can calibrate it or use a different instrument.

A 5m

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

B Error: e = (S1 - S2) - (S3 - S4)



26

How to Set up the Automatic Level 1. Take a look around and determine where you want to be able to shoot grades - the goal is to set up as few times as possible. 2. Find a solid, level area on the ground to set up your tripod. 3. Set the foot screws at the half way points.

4. Set up the tripod in the chosen location. Secure the feet and try to get the top of the tripod as level as possible. Make sure the feet are firmly pressed into the ground. Double check that the tripod is secure and will not shift when placing. 5. Place and level the instrument on the tripod.

A. Connect the instrument to the tripod via the center bottom screw instrument (not depicted above).



B. Level the instrument by using the foot screws until the bubble is in the center of the level shown above.



C. Double check that the instrument is level by turning it 180 degrees and checking that the bubble is still centered.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



27

How to read the Level Rod The following is an example of one type of level rod, and example elevations given in meters.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



28

How to Set and Level Benchmarks The following are steps on how to establish benchmark (BM) elevations. This should be done prior to determining elevations of any of the intermediate points. 1. When setting BMs, choose locations that will not be easily destroyed: A. Chisled “X” in rock B. PK nail in rock C. Nail in tree root, etc. 2. Set at least one BM per tower side. 3. Set up the level between the points. 4. Backsight BM#1 (the BM you set as elevation 100.00). 5. Add the recording to the BM’s known elevation getting Height of Instrument. 6. Foresight BM#2. Subtract the recording from the HI getting BM#2’s elevation. 7. Pick up and move the level. 8. Start from BM#2 and level your way back to BM#1. Your arithmatic should check back to BM#1’s known elevation (=100.00).

Below are sample field calculations for setting your benchmarks. STA

BS

HI

(+) BM#1

2.34

102.34

Notes

100.00 2.83

1.55

Elev

(-)

BM#2 BM#2

FS

101.06

BM#1

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

1.06

99.51 99.51

Turn Point

100.00

*BM#1 = 100.00 Checks



29

How to Run a Level Circuit

Establish Elevation

The following are steps to run a level circuit. Level circuit is the term used when surveying elevations that are all referenced from a known benchmark. We will assign an elevation of 100m to BM#1 and measure everything relative to that elevation. The process requires a minimum of two people: one person at the automatic level to sight points, and one person to move from point to point with the level rod. 1. Set up your tripod and level at a location where you will be able to see as many of the points you set when determining the Horizontal Control. 2. Backsight (BS) the benchmark that you assigned an elevation “100.00 m” and record this in your survey log. 3. Add the BS to the known elevation of BM#1 (100.00m) to get the height of instrument (HI). 3. Foresight (FS) elevations where known elevations are required, i.e. survey points. 4. Subtract FS elevations from the HI elevations to determine the elevations of these points. 5. Always end your circuit with foresight to a benchmark. Finally, subtract the last FS of BM from your HI. This elevation should be the same as the known elevation of the point.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



30



Moving the Level

You will not always be able to see all of the points you need from one set up. In those cases, do the following; 1. After step 5 from How to Run a Level Circuit, you can pick up your level and move it to your next location. 2. Have the person with the level rod stay at the last point you measured. 3. Once the level is set again, BS your last point. 4. Add that elevation to the last point’s elevation to create a new HI. 5. You can then proceed and FS points where elevations are required. 6. Always end your circuit by a FS to one of your BM’s. Finally, subtract your last FS figure from your HI. Your elevation should be the same as the known elevation of the BM.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY

Example Below are sample field calculations for how to run a level circuit with one instrument move. STA

BS (+)

HI

BM#1 Point A Point B Tower R Point C Point D Tower L Point E Point F BM#2

3.24

103.24

2.55

102.27

FS (-)

3.05 2.98 2.95 3.52 2.01 2.15 2.42 2.63 2.76

Elev

100.00 100.19 100.26 100.29 99.72 100.26 100.12 99.85 99.64 99.51

Notes

Turn Point

BM#2 = 99.51 *BM#2 Checks



31

2.4

SOIL AND ROCK IDENTIFICATION

For either side of the bridge one must determine the type of anchorage best suited for the geological area. As such, the first step of classification is to differentiate between soil and rock. Note the surrounding area; even if there is soil on top, there could still be rock at a shallow depth. Check for visible signs of rock. An easy way to make this determination is to assess whether or a not 2m deep hole can be dug with a shovel in the area of your anchors and/or foundations. If it is possible to manually dig a 2m hole, you have soil. If it is not possible to manually dig a 2m hole, it is likely you have rock. Use the following information in association with the Soil and Rock Identification Worksheet to determine what type of soil or rock is located at your site. Further determination of soil and rock characteristics may be valuable information for foundation, pedestal and anchor designs if diverting from B2P’s Standard Drawings.

Soil Classification Standard soil identification begins by determining if the soil is coarse-grained or fine-grained, depending on if greater than 50 percent of the material is larger or smaller than a 200# sieve respectively (roughly the size of a standard 0.074 mm window screen). If more than half of the soil can pass through a 200# sieve the soil is fine grained, if less than half can pass, the soil is coarse grained.

If the soil is coarse grained, estimate the amount of soil that is larger than 6mm diameter (about the size of a pencil eraser). If more than half is 6mm or larger, it is a gravelly soil. If less than half is 6mm, it is a sandy soil. Also see the chart on the next page for coarse grain ratios.



If the soil is fine grained, prepare a moist ball of soil about the size of large coin. Cut the ball with with a knife. If the ball cuts smooth and is shiny, the soil is a clay. If the ball cuts rough and looks scratched or dull, the soil is a silt.



Use the table in the next page to help determine what type of soil is present and what percentage is coarse grained at your bridge location, and fill in the information on the Soil and Rock Identification Worksheet.



Rock Classification If the bank is rock or highly consolidated soil, investigate by taking a hammer or other metal object and striking the surface. If the the result is a high-pitched, metallic noise, the rock is considered a hard solid rock. If the rock produces a thudding noise, or fractures into layered sheets, the rock is a soft and/or fractured rock. If this is the case, you cannot use a rock anchor.

Use the soil classification table to help determine what type of rock is present at your bridge location and fill the information on the Soil and Rock Identification Worksheet found in the Technical Survey.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY





32

Soil Classification The following table should be used to determine type of soil and corresponding anchor type.

Soil Type Coarse Grained Soils: Less than half of the soil can pass thorugh 200# seive, or thorough a typical 0.074mm window screen

Fine Grained Soils: More than half of the soil can pass thorugh 200# seive, or thorough a typical 0.074mm window screen

How to Identify

Anchor Type

Gravelly Soils

More than half of the soil particles are larger than 6mm, or a pencil eraser

Gravity Anchor

Sandy Soils

More than half of the soil particles are smaller than 6mm, or a pencil eraser

Gravity Anchor

Silty Soils

When a moist soil ball is cut with a knife, cut surface is rough, scratched and dull

Gravity Anchor

Clay Soils

 When a moist soil ball is cut with a knife,  cut surface is smooth and shinny





Gravity Anchor

               The table to the right is useful when determining the percentage of  coarse grains in a soil. The bottom right shows a good example  of  a soil with 50% coarse grains. Anything more than this is a coarse soil, anything less than this (shown in the table) is a fine  soil.   

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY





33

Rock Classification The following table should be used to determine type of soil and corresponding anchor type. Rock Type

Examples

How to Identify

Hard Rock

Quartzite Limestone Granite Dolomite etc.

Gives metallic, high pitched, sound when struck by hammer

Soft Rock

Phylite Slate Siltstone Claystone Schisy etc.

Does not fracture or break into layered sheets

Gives dull, low pitched, thudding, sound when struck by hammer Does fracture or break into layered sheets

Anchor Type

*Drum Anchor

Gravity Anchor

*If excavation through rock is at all possible (by means of pick axe, jackhammer, or other) a gravity anchor is preferred.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



34

TECHNICAL SURVEY 35

Sketch profile:

TECHNICAL SURVEY 36

Survey Information Abney Level

Survey Station

Topo Point

Distance (m)

Angle Theta ( +/- degrees)

Remarks

Horizontal Distance [Cos(theta) x distance]

Vertical Distance [Sin(theta) x distance]

Change in Elevation from Survey Station 100 (start point)

TECHNICAL SURVEY 37

Survey Information Automatic Level Station (STA)

Backsight (BS) (+)

BM#1

Height of Instrument (HI)

Foresight (FS)

Elevation

Notes

100.00

Assumed BM#1 Elevation

(-)

TECHNICAL SURVEY 38

TECHNICAL SURVEY 39

TECHNICAL SURVEY 40

SECTION 3: SELECTION OF BRIDGE DESIGN

3.1

INTRODUCTION TO BRIDGE TECHNOLOGIES

A footbridge is for the sole purpose of pedestrian traffic, including pack animals, bicycles, motorcycles and for certain bridge designs, carts. There are several designs for a pedestrian bridge, each applicable for different terrain types and usage needs. To the right is a summary of pedestrian bridge technology types. Bridges to Prosperity (B2P) primarily works with cable bridges, of which there are suspended and suspension design types. The cable suspended bridge is the most economical of the cable bridge designs, but has limited application in flat terrain.

3.2

SUSPENDED-CABLE PEDESTRIAN BRIDGE

The suspended-cable pedestrian bridge is based on traditional designs found in Nepal and Peru. The cables hang from short masonry towers. The bridge is suitable for short to mid spans in flood plains and short to long spans in gorges. The suspended pedestrian bridge is relatively easy to design and build, allowing minimum engineering supervision and maximum community participation.

B2P Suspended Bridge Design

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



41

3.3

SUSPENSION-CABLE PEDESTRIAN BRIDGE

The suspension bridge is a cable bridge which utilizes load bearing cables above the deck that are strung across high towers with a cambered deck. This design is most suitable for use in flat river terrain or in flood plains. Timber or steel towers may be constructed, but due to the complexity of design, an engineer must lead the project from design to implementation. For further information on this design, please refer to B2P’s website and Volume 4 of the Bridge Manual.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



42

SECTION 4: OTHER STRUCTURES The following are brief explanations of additional structures that should be considered during design. Note that this section is not intended to be all encompassing, and is only a starting point.

4.1

Typical windguy arrangement

WIND GUYS

Wind guys are required for any span exceeding 120 meters and at bridge sites with extreme wind conditions as deemed necessary by the design engineer. The suspended bridge herein is designed to withstand a 160 kilometer per hour wind load without any additional lateral support. Wind guys significantly increase the cost of the bridge as two (2) additional cables, considerable additional cable clamps and four (4) additional anchorages are required. When windguys are needed: • Additional topographic information is needed up and downstream from the bridge center axis, typically a distance equal to 10% of the span. • Additional geotechnical site-investigation is also required for each anchor location. For design material on wind guy structures, see Helvetas Trail Bridge Design Manual, located on B2P’s website, and in other engineering references.

4.2

Drainage System

DRAINAGE

Slope protection and drainage systems are required at sites when excess run-off may influence the slope stability. We recommended avoiding sites where instability is prevalent. If unavoidable, it is necessary to drain out the runoff and seepage to ensure the stability of the slope and to avoid the scouring of these structures. Water should be collected as closely as possible to its origin and navigated away from the bridge structures. This may require a surface catch drain on a slope, drainage around the structure, or both. The diagram to the right details subsurface and surface drainage systems.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



43

In the areas directly affected by seepage, sub-surface drainage may be required around the anchorage and/or foundation areas. A recommended sub-surface drain system is shown below. If excavation finds sitting water (picture bottom right), subsurface drainage is a must. Subsurface drains

filter cloth

Additional surface drainage channels assist in redirecting unwanted surface water. The geometry of such structures should be similar to either of the figures below. To avoid scouring to the drainage channel, additional protection in the form of protection walls and or sheeting should be considered.

Surface drains

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



44

4.3

RETAINING STRUCTURES Retaining walls are necessary when soil or highly weathered rock rise above the anchorage at slopes exceeding 1:1. There are many types of retaining structures, including rip-rap (see photo to right), gabion walls, dry stone, and traditional masonry walls. When the slope is too steep for rip-rap, dry stone retaining walls typically are preferable as they require only local materials and are constructed with the least amount of additional cost. Timber wall designs are also readily available, but require subsurface drainage. Below right is one example design using rebar to stake together timber and bracing into the hill slope. Recommended dry stone design parameters are listed below in the table. Depending on the topography of the site, the slope of the walls may vary greatly. A maximum height of dry stone wall is suggested to be no greater than 6 meters and used when hill slopes are no greater than 35 degrees. Sites with greater slope angles should not be considered, as stability issues are likely.

Drainage behind retaining wall

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



45

4.4

RIVER BANK PROTECTION River training structures should be avoided, as they are only a temporary solution and require frequent maintenance. Normal bridge abutment placement should be well back from river channels thereby eliminating the need for the same. River bank protection should be used when a river meanders and at locations where the bridge foundation would be susceptible to river scour. One such scenario would be if the bridge was placed at a river bend. As river bends are not recommended for crossing sites, river training structures should not be considered. Gabion walls are the most common type of river bank protection and are commonly used with simple span bridges to create a flush abutment surface. Filling the gabion walls requires considerable time and effort by the community and must be accounted for during planning stages of bridge construction. Gabion walls are generally designed as gravity structures, which use their own weight to resist earth and water pressures. Horizontal layers of wire mesh cages may be stepped either on the front or back side depending on the required application. An engineer is required to design the structure and specify the fill material. The fill material must have both strength and durability to resist the effects of water and weathering. Typically 8cm to 25cm diameter stone is specified, and if well-graded stone-fill is specified, the volume of stone required to fill the casing is nearly the volume of the empty containers.

VOLUME 2: FEASIBILITY & TECHNICAL SURVEY



46

BRIDGE BUILDER MANUAL

VOLUME 3

SUSPENDED CABLE BRIDGES

Volume 3: Suspended Bridge

Part F O U R1 TDesign H E D I T&I OAnalysis N

1

BRIDGE BUILDER MANUAL 2014

VOLUME 3.1

SUSPENDED CABLE BRIDGE

DESIGN FOURTH EDITION

2014

SUSPENDED PEDESTRIAN BRIDGE MANUAL Introduction The designs included in the Volume 3 Suspended Pedestrian Bridge Manual originated with Helvetas Nepal’s Short Span Trail Bridge Handbook that reflects Helvetas’ experience building more than 3,400 bridges over the past 30 years. By taking the suspended bridge design around the world, B2P hopes to honor Helvetas’ leadership in addressing the global challenge of rural isolation. In 2003, the Bridges to Prosperity (B2P) staff traveled to Nepal to train with Helvetas to learn about their cable-suspended bridge technology. In addition to learning about design and construction of the suspended bridge, Helvetas also taught B2P their approach to participatory bridge building at the community level. B2P has introduced this highly efficient and economical suspended footbridge design to countries in need of this technology all around the world. B2P has encountered new technical and cultural challenges as we have taken the technology from Asia to Africa, and then to Latin America. The designs have been modified and adapted to better suit local conditions in each given area of work. B2P has modified construction practices and expanded flexibility in design alternatives and design process materials to ensure that the suspended pedestrian bridge remains a locally sustainable option for communities in varying topographic and geographic regions of the world. There are four sections in Volume 3: Suspended Pedestrian Bridge Manual, structured as follows:

Part 1: Design and Analysis



Part 2: Technical Drawings



Part 3: Construction Guide



Part 4: Operations & Maintenance

As with any modulated design, usage assumptions must be made by the bridge designer. The following manual will attempt to provide both modulated drawings and design guides for those interested in bridge uses not covered within these manuals. For further design and loading assumptions, please reference the Helvetas Nepal Short Span Trail-Bridge Technical Handbook as well as internationally accepted design standards and locally pertinent design codes and standards. Terms of Use and Disclaimer No representations or warranties are implied or expressed herein. In consideration of this manual being provided gratis to others, all users agree to allow a listing and brief description of footbridges built with this manual on the B2P website, so that others in the same geographic region can visit such bridges for observation and training. Furthermore, all users agree to hold B2P, its employees, partners, sponsors, contractors and agents harmless from any and all liability arising from the use or application of the information provided herein.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

VOLUME 3 SUSPENDED PEDESTRIAN BRIDGE Part 1: Design and Analysis Table of Contents Section 1: Suspended Bridge: Design Background 1.1 Design Criteria and Material Properties 1.2 Cable Analysis 1.3 Anchor Analysis 1.4 Foundation Analysis 1.5 Suspender (Hanger) Analysis 1.6 Timber Decking & Crossbeam Analysis 1.7 Factors of Safety 1.8 Manual Limitations

Section 2: Suspended Design Procedure

2.1 Overview 2.2 Abney & Auto Level Survey 2.3 Bridge Profile & Fix Foundation Location 2.4 Calculate Required Number of Tiers 2.5 Finalize Position of Foundations 2.6 Select Tier & Anchors Designs 2.7 Select Cable Sizes: Cable Lookup Tool 2.8 Select Construction Drawings 2.9 Compile Final Drawings 2.10 Design Example 2.11 Design Example with Drafting Tools



Section 3: Material Estimate

3.1 Cable & Clamps 3.2 Steel Reinforcement Bar 3.3 Concrete 3.4 Decking 3.5 Other Materials 3.6 Material Quantities Example



Volume 3: Suspended Bridge

Part 1 Design & Analysis

SECTION 1: SUSPENDED BRIDGE: DESIGN BACKGROUND

The following section details basic design criteria and assumptions used by Bridges to Prosperity when modifying and extrapolating upon the B2P Standard Drawings. This section is intended for use in design verification and PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT need not be referenced for non-engineer designers, as all modular designs have already considered the following codes and assumptions. For typical bridge project use, skip to Section 2: Bridge Design Process.

1.1

Design Criteria & Material Properties Bridge Layout

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT



Minimum Freeboard = 2.0 m (floodplains) = 3.0 m (gorges) Minimum Setback

= 3.0 m or 35 degrees from bank (for soil) = 1.5 m or 60 degrees from bank (for rock)

Maximum Span

= 120 m

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT



Design Sag The Design Sag, B d , is assumed 5% throughout this manual. B d is a percentage value that must be multiplied by the span length to find the sag height value, h sag , discussed later in this section.

h sag is used to calculate the Lowest Point of Cable (f) as shown below. Freeboard can then be

calculated as the distance between the high water level and the lowest point of the cable.

Note: While preparing for construction, the Hoisting Sag B h is used when calculating sag height which is then used in calculating the Distance to the Lowest Point of Cable (f). This reduced sag for hoisting accounts for elastic stretch of the cable when load is applied. No additional cable stretch is assumed as cable is typically re-purposed. Maximum Height Difference (∆H)

ΔH ≤ Span 25

Distance to Lowest Point of Cable (f)

f=

(4 ⋅ hsag − ΔH )2 (measured from low side) 16 ⋅ hsag

Deck Width = 1.0 m Walkway Width = 1.9 m

(measured at handrail cable)

Volume 3: Suspended Bridge

Part 1 Design & Analysis

5



Design Loads

Assumed Material Unit Weights Steel = 7850 kg/m3 = 490 lb/cf Concrete = 2400 kg/m3 = 150 lb/cf Gabions = 1600 kg/m3 = 100 lb/cf Timber = 900 kg/m3 = 60 lb/cf General Soil (sand) = 1800 kg/m3 = 110 lb/cf Dead Load The actual dead load of the bridge is to be based on material takeoff. For both the B2P Suspension and Suspended bridges,100 kg/m (for a 1m wide deck) is a reasonable assumption. DL = 100 kg / m Live Loads Reference AASHTO Guide Specification for Design of Pedestrian Bridges, 1997. Note: Newer versions increase the design live load to 90 psf, a measure not adopted by B2P. Distributed Live Loads: Assuming 1.0 meter deck:

LL = 415

kgf 4.57 ⋅(0.25 + ) 2 m L

≥ 320 kgf m 2 (65 psf ) ≤ 415 kgf m 2 (85 psf ) L = Span(m)

Point Live Loads: The deck system shall support this point load anywhere between suspenders: PL = 226kgf (500 lb) Base Wind Load: The base wind load is the pressure resulting from a 100 mph wind kN WF = 1.7 2 (500 lb) m kgf Wind WL = Load: 30 kN (500 lb) 1.7 ofma2 typical (500 lb) InWF the=case suspended bridge, the linear loading on the bridge can be taken as the m following:

WL = 30

kgf (500 lb) m

Reference Helvetas Short Span Trail Bridge Manual (2003), SSTB-D type for additional information. Load Combinations DL + LL (applicable for most components) DL + LL + WL (applicable for loaded windguy design) DL + WL (applicable for unloaded windguy design)



Material Properties

Determine actual strength values via certification and or testing. B2P otherwise assumes the following strengths:

' Concrete: f c = 15 MPa ' f c = 10.3 MPa

= 2200 psi (mixed by drum mixer, or other) =1500 psi (mixed by hand)

Volume 3: Suspended Bridge

Part 1 Design & Analysis

6

Steel Pipe:

fy

= 240 MPa

= 35 ksi

Steel Reinforcing:

fy

= 275 MPa

= 40 ksi

Timber: fb = 3.96 MPa = 575 psi f v = 1.44 MPa = 210 psi q allowable Soil: = 143 kPa = 3,000 psf Y = 1.8T/m3 = 112 pcf φ = 33 degrees Cable/Wire Rope: Per certification: If using re-purposed wire rope, a certified breaking strength can be attained through load testing the cable at the section showing its greatest wear.

1.2

Cable Analysis Overview

Though the cable’s geometry most closely resembles that of a catenary curve, it can be analyzed as a parabolic curve for simplicity. There are three sag values to consider when designing the main cables for a bridge: Hoisting sag, design sag and breaking Sag. Hoisting sag is the resting position of the cable when it is only under its own weight. Design sag is the cable’s position under full dead load. Breaking sag is the sag of the cable under full dead load plus full live load. The typical values to be used for hoisting, design and breaking sag are 4.6%, 5% and 6.12% respectively. The breaking sag is increased to reflect elastic elongation in the main-span and backstays at full dead load and full live load. The increased sag will decrease the horizontal tension and therefore the overall tension in the cables so it should be used in sizing the main cables. Reference: Hanes Supply Catalog; Modulus of Elasticity for 6x19 IWRC EIPS, or other appropriate cable section.



Geometry and Forces

The following equations and diagrams describe the theory governing the geometry of the main span cables and the resulting forces. Phb = Ptb ⋅sin (α ) α = Angle of the cable on the backstay Pv = Pvm + Pvb



Phb = Ptb ⋅sin (α ) α = Angle of the cable on the backstay Pv = Pvm + Pvb



Horizontal Tension: P = ω c ⋅ L (kgf, equal throughout main span) h 2

8 ⋅ hsag

Distributed Load:

ω c = Total Distributed Load (

Sag Definition:

hsag = Bd ⋅ L

where: and:

Volume 3: Suspended Bridge

kgf ) m2 L = Span (m) Bd = 0.05 or 5% Part 1 Design & Analysis

7

Ptm =

Phm cos θ high



Total Tension (Main Span):



Vertical Tension (Main Span): Pvm = Ptm ⋅sin(θ high )



Angle to Horizontal (Main Span, Low Side):

Cable Angle Max (Main Span):

θ high = tan −1 (

Angle to Horizontal (Main Span, High Side):

θ high = tan −1

4 ⋅ hsag + ΔH ) (deg) L S 4 $ h sag + DH X L



i low = tan -1 $ S 4 $ h sag - DH X L P = P Total Tension (Backstay): tb tm



Vertical Tension (Backstay):



Angle to Horizontal (Backstay):



Horizontal Force (Backstay):

Pvb = Ptb ⋅sin(α ) Phb = Ptb ⋅sin (α ) α = Angle of the cable on the backstay Pv = Pvm + Pvb Phb = Ptb ⋅ cos(α )



Total Vertical Reaction (at Tower):

Pv = Pvm + Pvb



Cable Design



To determine the required number of cables, take the maximum tension in the cable per the above outlined process, multiply by the factor of safety (minimum 3.0) and divide by the breaking strength of the cables available. B2P provides a spreadsheet to assist in the determination of main cables. This topic is covered in greater detail in Section 2.7 of this Volume.



Available cable diameters and associated certified breaking strengths should be researched. Bridges to Prosperity Program Staff will provide certified breaking strengths of available inventory in B2P Program Countries.

Total Number of Cables Required: = Maximum Calculated Tension x FS Certified Breaking Strength of Cable



Resultant Force & Eccentricity

The geometry of the layout is also critical for the tower, tier and foundation design, and should be considered when finalizing the layout of a bridge project. The resultant force R (shown in the following diagram) of the cable, considering the backstay and main span components of the cable’s influence on the tower saddle, must remain within the kern distance for both the towers and the foundation tier. Eccentricity is measured from directly below the saddles all the way to the foundation tier (note that this does not correspond to the center of the towers nor to the center of the foundation tier). Equations dictating allowable eccentricity are as follows:

Tower Width Maximum Eccentricity (at Tower): E max - tower = 3 Maximum Eccentricity (at Foundation): E max - found. =

Found.Width 2

Angle of Resultant, β (from CL Tower): b = (90 - ( [(90 − α ) + (90 − θ )] 2 + i))

Volume 3: Suspended Bridge

Part 1 Design & Analysis

8

Eccentricity (at Tower): E tower = H tower $ tan (b) Eccentricity (at Foundation): E foundation = H found. $ tan (b)

1.3 Anchor Analysis Overview

This section describes the details of the deadman anchor design and associated assumptions. Rock anchor design discussion is beyond the scope of this manual. Refer to a licensed Professional Engineer for rock anchor analysis support.



In the case of the standard B2P design, the anchor is connected to the foundation and tiers via a continuously supported rock masonry wall. Note that these walls are imperative to the standard design and cannot be omitted without a thorough design check of the anchor acting by itself. Also note any assumptions made in regard to the existing ground conditions, as a lot of soil will need to be excavated in front of the anchor in order to safely bench or slope the excavations and to allow the cable to extend from the towers to the anchor at roughly the same angle the cables will be at when the bridge is complete.

If deviating from the standard designs, the following assumptions can be used when looking at the anchor acting by itself or acting with the foundation and tiers if walls or designed compression beams exist between the two: • Soil wall friction ( d ) is neglected as a conservative simplification. • Friction on the base of the foundation and approach walls is considered only when a compression member has been constructed between the anchor and foundation. Coefficient of friction, n = 0.45, between the earth and these components is recommended. • Soil is conservatively assumed to be sand and therefore assumed cohesionless (i.e. c = 0). • No consideration of earthquake design has been taken into account. • Backfill is required above the deadman anchor to provide the necessary resistance. Earth must be backfilled to the minimum required ‘Y’ dimension from the standard drawings before any live load is applied to the deadman. • Design has been completed assuming deadman anchors are in non-saturated conditions. Where a high water table is a concern, assume saturated condition is possible and deduct the buoyant force of the anchor beam and soil. • Assume there are no surcharge loads acting on the anchor.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

9



Passive and Active Earth Pressure



The principle forces acting on the deadman anchor are depicted in the following figure. This figure is referred to throughout this section. The principle modes of failure of the deadman anchor are sliding, uplift, and overturning, although the latter of the three is typically judged as an unrealistic mode of failure. Sliding and uplift are both checked herein, while overturning is deemed adequate via engineering judgement.



The forces acting on the anchor cause an active lateral pressure to develop behind the deadman (i.e. the earth exerts a force on the anchor – an additional force to the pull from the cable), and a passive pressure to develop in front of the deadman (i.e. the anchor exerts a force on the earth – the earth creates a resisting force to the pull from the cables). Since soils have a greater passive resistance, the earth pressures are not the same for active and passive conditions.



For a cohesion-less soil, the earth pressure theory of Rankine provides expressions for the active and passive earth pressure at a state of failure. The coefficient of earth pressure (K) is the term used to express the ratio of the lateral earth pressure to the vertical earth pressure (weight of the soil above).



If the embankment is level, the coefficients according to Rankine’s theory are given by the following expressions:

Active Earth Pressure Coefficient:

1 - sin (z) (unitless) K a = 1 + sin 1 + sin (z) 11 + sin (z) (unitless) + sin Kp = 1 - sin (z)

Passive Earth Pressure Coefficient: % where z is the internal angle of friction, assumed 33 .

The lateral earth pressures acting on the anchor are equal to the area of the trapezium along the height H 4 :

1

2 kN Active Earth Pressure: Pa = K a ⋅ γ ⋅ H 1 [ m ] 2

1 K p ⋅ γ ⋅ H 12 [ kN m ] 2 The resultant forces on the anchor due to the pressures act at 1 the height from the base of the anchor, and are 3

Passive Earth Pressure: Pp =

given as the following: Force due to Pa : F Q K aV = Pa $ L !kN $ Force due to Pp : F Q K pV = Pp $ L !kN $ where L is the length of the anchor.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

10



Frictional Forces Friction will also be helping to resist any movement of the anchor. In the typical case when the anchor is connected to the abutment, frictional forces can be considered to act on all of the elements. Depending on the demand, different friction values can be used for varying parts. For the anchor, use a frictional coefficient for concrete sliding on soil (~ 0.45 ), but if more resistance is needed, the material of the approach can be treated as soil on soil, rather than concrete on soil. Note: If separating the sections for analysis, be careful to not count any of the mass twice, or to omit the mass of the abutment. The vertical force from the cable can also be added to the overall weight of the tiers and towers. If the anchor is not connected to the abutments as recommended, friction should only be taken as acting on the bottom side of the anchor. The following is an example equation for the frictional forces, but assumes one coefficient of friction. Consider additional coefficients of friction and mass as necessary.

Total Vertical Load: Resisting Force Due to Friction:

W total = W foundation + W tiers + W towers + VPB v F Q Ff V = W total $n



Anchor: Check Against Sliding



When checking the anchor or whole abutment against sliding, sum all of the resisting forces and divide by the demand from the cables. The result should be greater than 1.5.

Factor of Safety (Sliding):

F (K p ) = F Q K V + P ≥ 1.5 a h



Anchor: Check Against Uplift



A check of the deadman anchor for safety against uplift is calculated by resolving the forces acting on the anchor and ensuring that the vertical resisting forces are at least 1.5 times greater than the vertical driving forces (i.e. a factor of safety of 1.5).



Factor of Safety (Uplift): =

QW soil + W conc.V ≥ 1.5 P v



Water Table and Buoyant Forces



If the water table rises above the base of the deadman anchor, the unit weights of the soil and concrete must be taken as buoyant unit weights i.e. typical unit weight of the material minus the buoyant force acting on the material. The buoyant force is equal the amount of water displaced. In the case of concrete, it can be assumed that it will displace 100% of its volume that is submerged whereas soil will displace approximately 60% of its volume that is submerged. As such, the submerged situation will significantly decrease the resisting forces.



Depending on the duration of the submerged case, the factor of safety may be reduced. For a Temporary Case (referring to a single event in a season), F.S. = 1.0. For a Long Term Case (referring to the entire rainy season), F.S. must remain = 1.5. Seek support from a Professional Engineer for all saturated cases.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

11

1.4

Foundation Analysis Overview All of the vertical forces generated in the cables are transferred through the towers and tiers into the foundation, in addition to the extra loading generated from the self-weight of the towers. To perform satisfactorily, the total distributed load generated must not exceed the bearing capacity of the soil. The load per unit area of the foundation at which shear failure in soil occurs is called the ultimate bearing capacity ( q u ).



Some of the general assumptions used throughout the design process that may be of interest to the Professional Engineer verifying or otherwise modifying B2P modular designs are below:

• No consideration of earthquake design has been taken into account. • Design has been completed assuming foundations are constructed on level ground. • Design has been completed assuming foundations are in non-saturated conditions. Where saturated conditions are of concern, deduct the buoyant force of the soil.



Design Calculations



The allowable soil bearing capacity q allow is the maximum bearing stress that can be applied to the foundation such that it is safe against instability due to shear failure. Specific values for the allowable should be determined for your soil. The designs in this manual assumes allowable soil bearing, q allow = 3,000 psf.

The maximum bearing stress ( q max ) is calculated by summing the total vertical load on the foundation (total vertical tension at the towers plus the self weight of the foundation, tiers, and towers) and dividing by the area of the foundation. Maximum Bearing Stress: The allowable bearing capacity is calculated from the ultimate bearing capacity, using a factor of safety of 2.0.

qmax =

1.5

W foundation + Wtiers + Wtowers + Vc Total Bearing area of Foundation

Factor of Safety (Shear):

q allowable ≥ 2.0 q max

Suspender (Hanger) Analysis Overview In order to design the suspenders, a safety factor of 5.0 should be used. The increased factor of safety is to account for the likelihood of cyclical bending and thus, repeated yielding of the steel during installation. The increased factor of safety is also to help account for the likelihood of corrosion of the steel over time. Based on the loads and yield strength assumed, B2P recommends no less than a 10mm deformed reinforcing bar for suspenders or #3 bar. Smooth rebar often is of inferior quality and strength, and should thus be avoided. The 10mm ribbed reinforcement bar provides an excessive factor of safety when considered only static loading, but has been sized to withstand corrosion over the design life of the bridge. Furthermore, the bars are oversized as a single suspender (hanger) failure will result in increasing the tributary load on neighboring suspenders, thereby inducing progressive failure.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

12

1.6

Timber Decking & Crossbeam Analysis



Design Calculations For the calculation of member capacity the following equations have been used:

Overview The B2P standard timber cross beams and decking boards have been designed according to NDS 2005. NDS designs using Allowable Strength Design. These boards for crossbeams and the deck need to be sized to support the design loads. With timber design it is typical to compare demand stress to allowable stress rather than comparing shear forces or moments.



Maximum Shear Due to Distributed Load:

Vdistributed = W c L 2 P V po int = 2

Maximum Shear Due to Point Load:

W c L2 Maximum Moment Due to Distributed Load: M distributed = 8



All assume the structure is simply supported 1m lengths, which is a conservative assumption.



PL M po int = 4

Maximum Moment Due to Point Load:

Check against Bending Moment To design both the crossbeams and the decking, the actual stress in the member due to bending must be less than or equal to the allowable stress of the given material. Timber material properties for the actual types of timber should be referenced from local suppliers. B2P assumes Fb = 3.96 MPa for allowable stress in bending.

Stress due to bending: fb ≤ F b' l CfC ui C irC CrcC CcfC f fu Where: F b = Fb C d C m C t C L C F C v C F = b allowable stress in bending C d = load duration factor (assume 1.25) C f = shape factor (assume 1.2) CL C m C = tmoisture factor (assume 0.97 for moisture >19%) =c other factors (assume 1.0) C C C C C m C t C L F v ffuu C i C r C fb = actual stress in bending

M max M S (where greater of2 M dist. or po int is used) S = Section Modulus = bd 6 fb =

Check against Shear To design both the crossbeams and the decking, the actual stress in the member due to shear must be less than or equal to the allowable stress of the given material. Timber material properties for the actual types of timber should be referenced from local suppliers. B2P assumes Fv = 1.44 MPa for allowable stress in shear. fv ≤ F v' Stress due to shear:

F v = Fv C d C m C t C i Where: Fv = allowable stress in shear C d = load duration factor (assume 1.25) CL C m C = tmoisture factor (assume 0.97 for moisture >19%) C m C t C i = other factors (assume 1.0) l

Volume 3: Suspended Bridge

Part 1 Design & Analysis

13

fv = actual stress in shear

fv = V $ 3 (where greater of Vdist or V po int is used for rectangular 2bd members)

1.7

Factors of Safety

Overview For the design of the main cables: FS = 3.0 For the design of bridge suspenders: FS = 5.0 For design of “deadman” anchors, use conventional passive/active soil resistance methods. Where saturated conditions are of concern, deduct the buoyant force of the anchor beam and soil above it. Note, a long term saturated condition refers to the entire rainy season, while a temporary saturated condition refers to a single flooding event. • Anchor Sliding: FS = 1.5 (Unsaturated) FS = 1.5 (Saturated, long term) FS = 1.0 (Saturated, temporary) • Anchor Uplift: FS = 1.5 (Unsaturated) FS = 1.5 (Saturated, long term) FS = 1.0 (Saturated, temporary) For the design of bearing capacity of the foundation: FS = 2.0

Design of all other structural elements shall be per recognized design codes using Safety Factors consistent with Allowable Stress Design methodology.

Referenced design codes include; • AASHTO Guide Specification for Design of Pedestrian Bridges, 1997. • Building Code Requirements for Structural Concrete (ACI 318-11) and Commentary. • AISC (American Institute of Steel Construction) Steel Construction Manual, 13th Edition. • NDS (National Design Specification) Supplement, Design Values for Wood Construction, 2005 Edition.

1.8

Manual Limitations

The suspended bridge is intended for pedestrians, livestock and narrow transportation aids (bicycles, wheelbarrows, etc.) capable of crossing on the 1.0 meter wide deck. Widening the deck up to 1.5 meters is possible with further engineering of the anchor, tower and decking plans, but any additional width in excess of 1.50m risks the inadvisable use by small cars. It is recommended that any bicycles, animals or motorbikes be walked across, but all are considered acceptable for crossing. Wood decking changes the deadload depending on the weight of the wood being used. If a steel deck is chosen, the corresponding deadload also changes. Although the lateral wind loadings proportionally increase with increased span, there is a design limit of 120 meters without wind guy structures and design by a Professional Engineer. The longitudinal rigidity of the bridge is compromised beyond 120 meters without the additional lateral support. Wind guys significantly increase the overall cost of the structure as two (2) additional cables and four (4) additional anchors are required. Contact Bridges to Prosperity for wind-guy design guides and tools.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

14

SECTION 2: DRAWING SELECTION PROCEDURE

This section outlines the steps in order to select appropriate drawings from B2P’s standard suspended bridge design drawings, found in Volume 3.2. This process does not require a technical background or any design calculations to be performed. All pertinent design assumptions and bridge geometries have been taken into account in the standard B2P suspended bridge drawings. For background information and design assumptions, refer to Section 1.1 in this Volume.

2.1 Overview

Designing the suspended cable bridge requires minimal technical background. The following section will provide a step by step guide to designing a bridge following the completion of the site survey as outlined in Volume 2: Feasibility & Topographic Survey.

2.2 Abney or Automatic Level Survey 2.3 Bridge Profile & Fix Foundation Locations 2.4 Calculate Required Number of Tiers 2.5 Finalize Position of Foundations 2.6 Select Tier & Anchors Designs 2.7 Select Cable Sizes: Cable Look-up Tool 2.8 Select Construction Drawings 2.9 Compile into Final Drawings 2.10 Design Example

2.2

Abney Level or Automatic Level Survey



If not done so already, complete a bridge profile survey using an Abney level or automatic level, as available. Reference Volume 2: Feasibility & Topographic Survey for complete details.

2.3

Bridge Profile & Foundation Locations



Create a profile sketch from the site survey. Use points ‘L’ (left) and ‘R’ (right) from the survey to mark the preliminary location of the towers for the left and right side respectively.



Verify that the left abutment shown in the bridge profile is referring to the left bank, when facing down stream.



Define critical components: • Span in meters. Note if measured between ‘L’ and ‘R’ or if intended mid-tower span • Height difference between ‘L’ and ‘R’, from elevation data on survey sheet • Note soil or rock type on either side See sample sketch on next page.



Volume 3: Suspended Bridge

Part 1 Design & Analysis

15

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Volume 3: Suspended Bridge

Part 1 Design & Analysis

16

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

2.4

Calculate Required Number of Tiers



Span (L) in meters (must be less than 120 meters) As the survey points ‘L’ and ‘R’ are relative to the front-of-foundation to front-of-foundation, start by assuming an additional 1.40 meters on either side to include walkway saddle to walkway saddle span. Once drawings are selected, verify the dimension, noting that it may change based on the finalized location of foundations.



Height difference ( DH ) = Elevation ‘L’ – Elevation ‘R’ Start by assuming that each side has one tier, so the elevation of the walkway towers is 1.40 meters above ‘R’ and ‘L’ respectively (1.0 meter for one tier, 40cm for saddle placement, per the tower drawing T1). Use the same elevation assumptions and nomenclature as used in the survey: low side foundation elevation = 100.00. Note: During final design, ensure the height difference ( DH ) is not greater than the 4% of span length, or L/25.

A minimum clearance is required between the lowest point in the cable and the highest point that the water has ever reached (HWL). Furthermore, the maximum height difference, DH , between the two towers must be no more than the span (L) divided by 25, or four percent of the span. If DH exceeds this amount, one or both of the towers needs to be raised. To provide adequate clearance and to equalize differences in elevation between two sides, one must calculate the required number of tiers. Each tier is 1.0 meter tall as the elevation of the bridge towers dictate the elevation of the cables. In order to calculate the required height, the following information must be known:

Cable Design Sag ( B d ) and Hoisting sag ( B h ) The Design Sag, B d , is assumed 5% throughout this manual. Design Sag, B d is used in the Distance to the Lowest Point of Cable (f) calculation, which in turn is considered to ensure proper freeboard above the High Water Level. While preparing for construction, the Hoisting Sag B h is used when calculating the Distance to the Lowest Point of Cable (f). This allows for cable hoisting at a higher elevation than expected due to the elastic stretch of the cable. No structural cable stretch is assumed, as cable is assumed repurposed. Re-purposed Cable (includes cable donated from B2P program) Percent of Span Design sag ( B d ) 5.00% Hoisting sag ( B h ) 4.60% Distance to Low point ‘f’ If both sides are equal height ( DH = 0), then the low point is directly in the middle and f will equal hsag. If not, calculate the actual distance to low point, f, using the following equation or using the low point matrix on the following page.

(4 ⋅ hsag − ΔH )2 f= 16 ⋅ hsag

Volume 3: Suspended Bridge

Part 1 Design & Analysis

17

Distance to Low Point ‘f’ Relative to low side abutment

Height Differential between abutments (m)

35 0.0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50

40

45

50

55

Span (m) 60

65

70

75

80

85

90

95

100 105 110 115

1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.05 4.09 4.32 4.55 4.77 5.00 5.23 1.63 1.88 2.13 2.38 2.63 2.88 3.13 3.38 3.63 3.88 3.93 3.97 4.19 4.42 4.65 4.88 5.10 1.51 1.76 2.10 2.26 2.51 2.76 3.00 3.25 3.50 3.75 3.80 3.84 4.07 4.30 4.53 4.75 4.98 1.40 1.64 1.89 2.14 2.39 2.64 2.89 3.14 3.38 3.63 3.68 3.72 3.95 4.18 4.41 4.63 4.86 1.29 1.53 1.78 2.03 2.27 2.52 2.77 3.02 3.27 3.52 3.57 3.61 3.83 4.06 4.29 4.51 4.74 1.18 1.42 1.67 1.91 2.16 2.41 2.66 2.90 3.15 3.40 3.45 3.49 3.72 3.94 4.17 4.39 4.62 1.08 1.32 1.56 1.81 2.05 2.30 2.54 2.79 3.04 3.29 3.34 3.38 3.60 3.83 4.05 4.28 4.50 0.98 1.22 1.46 1.70 1.94 2.19 2.43 2.68 2.93 3.17 3.22 3.26 3.49 3.71 3.94 4.16 4.39 1.36 1.60 1.84 2.08 2.33 2.57 2.82 3.06 3.11 3.15 3.38 3.60 3.83 4.05 4.28 1.50 1.74 1.98 2.22 2.47 2.71 2.95 3.00 3.04 3.27 3.49 3.71 3.94 4.16 1.64 1.88 2.12 2.36 2.60 2.85 2.90 2.94 3.16 3.38 3.60 3.83 4.05 2.02 2.26 2.50 2.74 2.79 2.83 3.05 3.27 3.50 3.72 3.94 2.16 2.40 2.64 2.69 2.73 2.95 3.17 3.39 3.61 3.83 2.30 2.54 2.59 2.63 2.85 3.07 3.29 3.51 3.73 2.44 2.49 2.53 2.75 2.96 3.18 3.40 3.62 2.43 2.65 2.86 3.08 3.30 3.52 2.55 2.77 2.98 3.20 3.42 2.88 3.10 3.32 3.00 3.22

Verify adequate Freeboard (Fb) Freeboard is the clearance required between the lowest point in the cable and the highest point of the water. An engineer may reduce or increase the suggested freeboard values in accordance with site topographic and hydrological conditions, but for general purposes, minimum freeboard clearance required is as follows: - Flood Plains: 2.0 meters - Gorges: 3.0 meters Freeboard is verified by taking the low side abutment elevation, subtracting the sag value ‘f’ and subtracting the elevation of the High Water Level. If the value of Freeboard is less than required, the designer must increase the number of tiers on either one or both foundations.

Fb = Low Ele. - f - HWL 2.5

Finalize Position of Foundations

After selecting the number of tiers required to achieve freeboard, the size of the foundation footprint is known per the drawings. This step will verify the layout. If front of foundation survey points ‘L’ and ‘R’ must be moved, take care to note on both the initial survey and at field site. • Verify adequate slope angle or distance from slope (Volume 2 Topographic Survey)

Volume 3: Suspended Bridge

Part 1 Design & Analysis

18

Maximum 35 degree slope in soil or minimum 3.0 meters from edge

Maximum 60 degree slope in rock or minimum 1.5 meters from edge

• Follow steps outlined in Section 2.4 with new Foundation location, height difference, sag and f values, to find updated Freeboard value. If the Freeboard ( Fb ) exceeds minimum, move forward with design. Example A flat valley surveyed with a span of 60 meters, point ‘L’ 2.0 meters lower than point ‘R’, and a High Water Level (HWL) at elevation 96.5 meters from the survey Low side elevation = 101.40 meters Low point in cable (relative to low side) ‘f’ = 2.08 meters

Fb = Low Ele. - f - HWL



= 101.40 - 2.08 - 96.5 = 2.82 > 2.0 OKAY

Volume 3: Suspended Bridge

Part 1 Design & Analysis

19

2.6

Select Tier & Anchor Designs There are two types of anchor designs; Gravity Anchors and Drum Anchors. Gravity Anchors may be used in any soil or rock conditions as they rely on self-weight and ‘deadweight’, or material placed over the anchor. As such, the excavation required is considerable. Drum Anchors require rock conditions as they rely on friction between the rock face and the poured concrete drum. As such, only hard or fractured rock conditions are acceptable. See Volume 2: Feasibility & Topographic Survey for more information. Gravity Anchor plans are split into two main subcategories; 0 - 60 meter spans, and 61 - 120 meter spans. Each classification includes one (1), two (2), and three (3) tier alternatives. A summary of Gravity Anchor Plans found in Volume 3 Part 2: Suspended Bridge Drawings are as follows:



0 - 60 m 1 0 - 60 m 2 0 - 60 m 3 61 - 120 m 61 - 120 m 61 - 120 m

1G60 2G60 3G60 1G120 2G120 3G120

Drum Anchor plans are only available through 60m spans. No further classification is needed as rock anchors do not lend themselves to more than one tier. This is due to the short distance between the anchor and the saddles, required due to sloped rock conditions. There are two sizes of drum anchors; small and medium. Small (0 - 40 meters) and Medium (41 - 60 meters) anchors are included in 1D60. Note: 60-120 meter projects in rock require design support from a Professional Engineer. A summary of Drum Anchor Plans found in Volume 3 Part 2: Suspended Bridge Drawings are as follows:



2.7

Tier Gravity Anchor Tier Gravity Anchor Tier Gravity Anchor 1 Tier Gravity Anchor 2 Tier Gravity Anchor 3 Tier Gravity Anchor

0 - 60 m

1 Tier Drum Anchor in Rock

1D60

Select Cable Sizes: Cable Look-up Tool Bridges to Prosperity created a Microsoft Excel Cable Look-up Tool, available at the website at bridgestoprosperity.org/resources. The Cable Look-up Tool requires the user to input the breaking strength (often referred to as breaking force) of available cable (in pounds), and based on any number of cable combinations, outputs the maximum span allowable for a given deck width. Before using the tool, research available steel cable and request a Proforma Invoice stating breaking strengths for available cables, and if using B2P repurposed cable, request breaking strength certifications from B2P Program staff. The Cable Look-up Tool assumes that the cable has a live load elongation (starting from dead load only) of 0.325% and is intended for use with repurposed cable (this includes cable sourced as part of B2P’s recycled cable donation program).



Step 1 Research available cable breaking strengths. If reported in metric tons or kilonewtons (kN), convert into pounds using the following relationships:

Metric Tons # 2204.62 pounds Metric Ton = pounds pounds = pounds kN # 224.81 kN

Volume 3: Suspended Bridge

Part 1 Design & Analysis

20

Step 2 Input Breaking Strength values (in pounds) and desired number of cables (red text), as shown in the following diagram.



Step 3 Modify combinations until desired deck width has value at least as long as bridge span (yellow). Example Given only 7/8” cable with 68,343 pound breaking strength, first input 3 walkway cables and 2 handrail cables. The span highlighted in yellow, beneath the 100cm deck width results in a span less than our 60 meter span. Try again with 4 walkway cables and 2 handrail cables. The allowable span shown is 64m, longer than our actual span, so this is acceptable.

Note: 3 and 5 walkway cable configurations are preferred, as this allows a center cable to support the crossbeam.

Step 4 Calculate quantity of cable. Refer to Section 3.1 Material Quantities, Cable & Clamps.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

21

2.8

Select Construction Drawings

Based on a given span length, geologic conditions and the number of tiers, two (2) Abutment Tier & Anchor drawings must be selected, one for each side of the river. The Tower drawing details the 1.0 meter deck width tower and is required. Three (3) Decking drawings must be selected for either 3 or 5 walkway cables, with options for both timber crossbeam with nailers and timber crossbeams with no nailers, respectively.

Abutment Tier & Anchor (Right and Left side required) Gravity Anchors 0 - 60 m 1 Tier 1G60 0 - 60 m 2 Tier 2G60 0 - 60 m 3 Tier 3G60 61 - 120 m 1 Tier 1G120 61 - 120 m 2 Tier 2G120 61 - 120 m 3 Tier 3G120 Rock Drum Anchors 0 - 60 m 1 Tier 1D60 Tower 1.0 m deck width T1 Decking Decking Plan 3 walkway cables W3.1 5 walkway cables W5.1 Decking Section 3 walkway cables W3.2 5 walkway cables W5.2 Decking Detail With Nailer 3 walkway cables W3.3 5 walkway cables with Nailer W5.3 No Nailer 3 walkway cables No Nailer W3.4 5 walkway cables No Nailer W5.4

2.9

Compile Final Drawings

Complete the bridge design by detailing a plan view of the specific project, and compile all required bridge drawings for the other details, as included below.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

22



Include the following critical dimensions and select the following drawings; Critical Dimensions Drawings Span Right Side Anchor (G series) Depth to anchor Left Side Anchor (G series) Distance to back of anchor Tower (T series) Deck width Decking Plan (D series part 1) Free board from HWL Decking Section (D series part 2) Sag (design and hoisting) Decking Detail (D series part 3) Height differential between abutments

2.10 Design Example

A flood plain valley with a 60 meter span was surveyed. Critical points of the survey are as follows: Point ‘L’ Elevation (low side) = 100.0 meters Point ‘R’ Elevation (high side) = 102.0 meters HWL = 96.5 meters To calculate the minimum number of tiers, modify until freeboard (Fb) is greater than 2.0 meter minimum as specified for a flood plain. Start by assuming one tier (1.0 meter tier height plus 0.4 meter saddle height above tier).

Span (L) = 60 meters

Elevation low side walkway saddle = 100m + 1.40m = 101.4m Elevation high side walkway saddle = 102m + 1.40m = 103.4m Height difference (∆H) = 103.4m - 101.4m = 2.0m L

60

DH < 25 = 25 = 2.4 > 2.0 Verify:

OKAY

Distance to Low point ‘f’ = Cable Design Sag (Bd) = 5% of span = 60 $ 0.05 = 3.0m 2 Low Point f = (4B d - DH) = 2.083

16B d

Or, cross reference span and ∆H on Design Sag Elevation Chart to find Distance to Low Point ‘f.’ For a 60-meter span, ∆H of 2.0 meters, the Distance to Low Point, ‘f’, relative to the low-side is 2.08 meters

Volume 3: Suspended Bridge

Part 1 Design & Analysis

23

35 0.0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50

40

45

50

55

60

65

70

75

80

85

90

95

100 105 110 115

1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.05 4.09 4.32 4.55 4.77 5.00 5.23 1.63 1.88 2.13 2.38 2.63 2.88 3.13 3.38 3.63 3.88 3.93 3.97 4.19 4.42 4.65 4.88 5.10 1.51 1.76 2.10 2.26 2.51 2.76 3.00 3.25 3.50 3.75 3.80 3.84 4.07 4.30 4.53 4.75 4.98 1.40 1.64 1.89 2.14 2.39 2.64 2.89 3.14 3.38 3.63 3.68 3.72 3.95 4.18 4.41 4.63 4.86 1.29 1.53 1.78 2.03 2.27 2.52 2.77 3.02 3.27 3.52 3.57 3.61 3.83 4.06 4.29 4.51 4.74 1.18 1.42 1.67 1.91 2.16 2.41 2.66 2.90 3.15 3.40 3.45 3.49 3.72 3.94 4.17 4.39 4.62 1.08 1.32 1.56 1.81 2.05 2.30 2.54 2.79 3.04 3.29 3.34 3.38 3.60 3.83 4.05 4.28 4.50 0.98 1.22 1.46 1.70 1.94 2.19 2.43 2.68 2.93 3.17 3.22 3.26 3.49 3.71 3.94 4.16 4.39 1.36 1.60 1.84 2.08 2.33 2.57 2.82 3.06 3.11 3.15 3.38 3.60 3.83 4.05 4.28 1.50 1.74 1.98 2.22 2.47 2.71 2.95 3.00 3.04 3.27 3.49 3.71 3.94 4.16 1.64 1.88 2.12 2.36 2.60 2.85 2.90 2.94 3.16 3.38 3.60 3.83 4.05 2.02 2.26 2.50 2.74 2.79 2.83 3.05 3.27 3.50 3.72 3.94 2.16 2.40 2.64 2.69 2.73 2.95 3.17 3.39 3.61 3.83 2.30 2.54 2.59 2.63 2.85 3.07 3.29 3.51 3.73 2.44 2.49 2.53 2.75 2.96 3.18 3.40 3.62 2.43 2.65 2.86 3.08 3.30 3.52 2.55 2.77 2.98 3.20 3.42 2.88 3.10 3.32 3.00 3.22



Verify Freeboard ‘Fb’ Fb = Low Ele. - f - HWL = 2.82 > 2.0 OKAY Select Cable The cable supplier provided specifications for a 26 mm IWRC cable with breaking strength of 30.0 metric tons (68,343 pounds). Using the Cable Look-up Tool, 5 walkway deck cables and 2 hand cables are required, as they are sufficient to a 64 meter span. Select Drawings One tier, 60 meters or less Right abutment = 1G60 One tier, 60 meters or less Left abutment = 1G60 Tower Drawing = T1 Decking Plan, 3 cable = W13 Decking Section, 3 cable = W23 Decking Details, 3 cable Nailer = W33 Compile into Final Drawing Set

Volume 3: Suspended Bridge

Part 1 Design & Analysis

24

2.11

Design Example with Drafting Tools

An alternative way to do a standard design is with the use of drafting tools. A flood plain has been surveyed and plotted below. The first step is to identify the constraints of the site. In the diagram below, a vertical dashed line has been drawn to indicate the minimum set back distance. Make sure that this minimum set back is also checked against the maximum slope from the high water level (HWL) to the front of the Foundation. In this case, the minimum setback controls the design.

Step 1

Once the constraints of the site are outlined, set the preliminary tower locations. In most cases, it is convenient to set the towers so that the span is a round number. These may need to be adjusted later depending on the site. Based on the survey, first try the smallest abutments possible: one tier on both sides. Once these are placed, quick dimensions can be done to get a general idea of the layout. In this case, all dimensions are as expected and meet the design criteria previously outlined.

Step 2

When the towers have been placed and all criteria are met, the next step will be to place the anchors. This can be done by extending a line from the top of the tower (hand rail saddle) towards the ground away from the of the river at a 24 degree angle (from horizontal). This line will represent the handrail cable and should extend past where the anchor will likely be.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

25

Step 3

In drawing the design, an easy way to place the anchor is to draw two dashed lines: one that is parallel to the slope of the ground that is offset by the required ‘y’ value (vertically) and the other that is parallel to the handrail cable on the backstay that is offset half of the height of the anchor (vertically). In this case with a 36m span, the required y-value and half the height of the anchor are 1.5m and 0.5m respectively. Where these two lines meet will mark the front, top corner of the anchor. This method works best if you are building on a slope (<10 degrees per the standard drawings). If the topography is flat, building up the material on top of the anchor (walls above ground) may be a better solution and could potentially reduce the materials needed.

Step 4

The final step is to draw in the approach walls and start assembling the quantities needed to build the project. Note that this step is not required but if this step is not done, the standard drawings should be printed out and marked up to represent the actual distances. As in the other example, the remaining drawings need to be selected and combined with the overall layout drawing.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

26

SECTION 3: MATERIAL ESTIMATE The following section details material quantity take-offs. This section is intended for use only with B2P suspended bridges and should not be referenced for modified structures.

3.1

Cable & Clamps Select steel cable based on cable breaking strengths and the Cable Look-Up Tool, available at bridgestoprosperity.org/resources, as outlined in Section 2. After initially selecting the optimum combination of cables for the given span, calculate the total quantity to order by multiplying the number of cables by the length of each cable, L cable .

L cable = 1.04 (L + 14 + d left + d right) This is an empirical formula developed through experience in the field. 14 meters provides excess horizontal length that is helpful while laying out cables (particularly in long-spans) and provides length to account for cable sag and wrap-back around the anchors. The distance between anchors and towers d left and d right can be found using B2P Construction Drawings and site topography.



Consider the costs of several combinations of cable before moving on. Often, cable is sold by the reel of 500 meters, so if one combination requires slightly more than 500 meters, it may be worth the additional cost to increase the size of the cable to reduce the number of cables and thus the total required length. The quantity of clamps per cable is dependent on the size of the cable and the type of clamp selected. The table below is the Bridges to Prosperity standard for torque requirements for drop-forged cable clamps at given cable and clamp diameters. Cable clamp manufacturer provide specifications that must be verified as this is included only as a guideline. Cable Diameter (inch) (mm) 5/8 16 3/4 19 7/8 22 1 25 1 1/8 29 1 1/4 32 1 3/8 35 1 1/2 38

3.2

Spacing (mm) 102 114 121 132 144 160 160 171

Drop-Forge clamps # of clamps Torque (ft-lbs) 3 95 4 130 4 225 5 225 6 225 7 360 7 360 8 360

STEEL REINFORCEMENT BAR Towers

- 4 pieces steel rebar, 19mm z (#6) x 4.50 meters in length - 3” angle iron x 67cm in length - Rebar guides for walkway cables: (optional) # of walkway cables + 1, 16mm x 20cm each - 4 x cut tire rims (2 complete tire rims)

Suspenders (hangers)

Volume 3: Suspended Bridge

Part 1 Design & Analysis

27

Suspenders (hangers)

- 2 x (Span + 1), minimum 10mm z (#3), deformed rebar (#3), cut to 2.0m length

Anchors: Gravity (Deadman) Beams Small/Medium anchor (up to 60m span)

Large Anchor (up to 120m span)

19mm z x 2.9 m

4

8

10mm z x 2.2 m

11 bent into square 0.5m per side

N/A

10mm z x 3.4 m

N/A

Rebar size

19mm z x 3 m

3 bent into U-shape for erection hooks

11 bent into square 0.8m per side 3 bent into U-shape for erection hooks

Anchors: Rock Drum (Drilled Pier) Spans 40 meters or less • Anchor rods, 16 pieces, 25 mm z , cut at 1.50 meters • Inner drum: 8 pieces, 10 mm z , cut at 3.40 meters, bent into 0.85 m



diameter circle • Outer drum: 8 pieces, 10 mm z , cut at 5.25 meters, bent into 1.45 m diameter circle

Spans 41-60 meters

• Anchor rods, 20 pieces, 25 mm z , cut at 1.50 meters • Inner drum: 8 pieces, 10 mm z , cut at 4.15 meters, bent into 1.10 meter diameter circle • Outer drum: 7 pieces, 10 mm z , cut at 5.90 meters, bent into 1.65 meter diameter circle

3.3 CONCRETE Refer to this section to calculate all concrete materials - cement, sand, gravel and relative water ratios. Bag quantities included herein assume 42.5kg bags. If local supply is provided in a different quantity, adjust estimates accordingly.

Masonry:

The quantities provided below are given to the 3G series but should be adjusted based on the actual drawing used. They include the 2 bags poured while grouting the interior of each tier and the capping of that tier. Foundation Tier 1 Tier 2 Tier 3

18 bags 16 bags 14 bags 12 bags

Towers (masonry) Approach walls Approach cap

Volume 3: Suspended Bridge

8 bags 16 bags (for 2m height) 16 Bags

Part 1 Design & Analysis

28

Poured concrete:

The proportions we recommend for poured concrete (anchor, towers fill, etc.) is 1:2:3 (cement: sand: gravel) and should be revised when needed based on the materials available. The sum of the ingredient volumes will be greater than the volume of concrete, because the sand will fill the voids between the coarse aggregate. The materials normally have 30% to 50% greater volume than the concrete mix. Clean water should be added on a visual and texture basis as outlined in Volume 3.3. If accelerant is to be used to expedite the curing time, take care to note the quantity required as specified on the product. When developing the project schedule, four days curing time for the anchor should be adequate, as the crushing load of the cable is only on the order of 250psi. Reference Volume 3.3 for additional detail.



3.4 DECKING Bridges to Prosperity uses wood decking when a sustainable source of wood is a viable option. If you choose to use metal or plastic decking, research and address deadloads accordingly. There are two wood decking options: with or without a nailer. The nailer is the same width as the decking panels, and is attached to the top of a narrower cross-beam to increase the amount of surface area available for nailing the decking panels. The nailer improves constructability and allows for a smaller crossbeam size while increasing the total length of decking panels required. Decking panels are to be cut to 3.0 meters for any span over 60 meters, and preferably all spans. If the bridge is shorter than 60 meter span, 2.0 meter decking panels are allowable. The total number of decking panels is equal to [span divided by length of each board (either 2.0 or 3.0)] multiplied by five (5), as there will be five decking panels across, each 20cm wide. If nailers are to be used, an additional (span plus one) meters of decking panels will be required, cut at 1.0 meters. Nailer (Recommended)



No Nailer



Quantities Crossbeams: (Span + 1) Decking: (Span / length of each board (either 2.0 or 3.0) x 5) Nailers (optional): (Span + 1)

Volume 3: Suspended Bridge

Part 1 Design & Analysis

29

3.5

OTHER MATERIALS Flexible plastic tubing: 3” diameter* Flexible plastic tubing: 2” diameter* Tie-wire Galvanized tie-wire U-nails/Staples Screws: 5/16 x 10 cm (4”) Anti-corrosive paint Fencing: 1.20 m high (4’) Roofing tar Handrail saddles or tier rims 67cm 3” angle iron / walkway saddles Sand / gravel Masonry block / Bricks

4 meter per cable (around adjustable anchor) 1 meter per cable (threaded over tower) 10 kg 5 kg 1 kg per 10 linear meters 5-6 per deck panel+ 4 per cross beam if using Nailer 1 gallon (3.8 L) per 50 linear meters Bridge span x 2 1 gallons 4 pieces 2/4 Varies based on design Varies based on design

* The best product for this purpose is reinforced tube, often found at plumbing stores.

Volume 3: Suspended Bridge

Part 1 Design & Analysis

30

3.6

MATERIAL QUANTITIES EXAMPLE

Bridge Location: Cahuac District, Huanuco Span: 60m Item Cable and clamps

Unit

Units required

Cable 26mm Clamps 26mm

m piece

391.04 64.00

bags of 40kg unit (9m) (9m) (9m) unit unit kg mts gal

173.66 180.00 6.00 11.00 4.00 4.00 4.00 10.00 20.00 8.00

piece piece unit kg (9m) gal mts kg kg

62.00 155.00 62.00 26.00 32.00 1.00 76.00 6.00 20.00

m³ m³ m³ m³

40.00 10.00 80.00 40.00

Transportation Transportation of materials

per trip

6.00

Labor and Technical Support Mason Supervision Logistical Support

daily daily per visit

180.00 90.00 12.00

Construction Materials Cement Concrete Blocks = 40 x 20 x 15 (cm) Rebar 10mm (3/8") Rebar 16mm (5/8") Rebar 20mm (3/4") Handrail saddles Walkway saddles - 2 cable Tying wire Plastic suction tube 3" Roofing Tar Deck Wood crossbeams - (10cm x 20cm) x 140cm Wood platform - (5cm x 20cm) x 200cm Screw - 8mm x 10cm(nailing panel to crossbeam connection) Nails - 15cm Smooth iron bar 10mm (3/8") (suspenders) Anti-rust paint (suspenders) Safety fencing = 1.5m in height U-Nails Tying wire Local Materials Sand Gravel River rock Dressed Stone

Note: For pricing estimate, local material and labor costs must be considered. Volume 3: Suspended Bridge

Part 1 Design & Analysis

31

BRIDGE BUILDER MANUAL 2014

VOLUME 3.2

2014

SUSPENDED CABLE BRIDGE

DRAWINGS FOURTH EDITION

BRIDGE BUILDER MANUAL 2014

VOLUME 3.3

SUSPENDED CABLE BRIDGE

2014

CONSTRUCTION FOURTH EDITION

INTRODUCTION Welcome to Volume 3: Suspended Bridge Manual, Part 3: Construction. This volume includes Safety, Quality Control and Construction for B2P cable-suspended bridges. Refer to Volume 1: Community Development, Volume 2: Feasibility and Topographic Survey, Volume 3: Part 1: Suspended Design, Part 2: Drawings and Part 4: Maintenance, and Volume 4: Suspension Bridge Manual, as necessary. Bridges to Prosperity (B2P) provides isolated communities with access to essential health care, education and economic opportunities by building footbridges over impassable rivers. We envision a world where poverty caused by rural isolation no longer exists. We build to INNOVATE by developing and sharing engineering solutions that are safe, replicable, and locally viable. We build to EDUCATE by providing educational programs that teach footbridge construction to reach the greatest number of people in need. We build to INSPIRE by providing opportunities for leadership development and personal growth through international collaboration.

Volume 3: Suspended

Part 3 - Construction Guide

VOLUME 3 SUSPENDED PEDESTRIAN BRIDGE PART 3: CONSTRUCTION GUIDE & QUALITY CONTROL Table of Contents Section 1: Construction Overview

Section 2: Safety

2.1 Travel member responsibilities 2.2 B2P Health and Safety 2.3 Safety in Project Planning 2.4 On-Site Safety 2.4.1 Safety System 2.4.2 Safety Culture 2.4.3 Near Hits 2.4.4 Personal Protective Equipment 2.4.5 Hand and Power Tool Safety 2.4.6 Fall Protection 2.4.7 Trenching and Excavation Safety



Section 3: Quality Control

3.1 Quality Control Overview 3.2 Quality Control Requirements 3.2.1 Photo Inventory 3.2.2 Quality Control Forms 3.2.3 As-Built Reports 3.3 Construction Material Quality Control 3.3.1 Concrete 3.3.2 Stone Masonry 3.3.3 CMU Masonry 3.3.4 Main Cable Inspection and Care 3.3.5 Clamping and Cable Crush



Volume 3: Suspended

Part 3 - Construction Guide

Section 4: Material Preparation

4.1 Required Materials 4.1.1 Local Materials 4.1.2 Delivered Materials 4.1.3 Materials List 4.1.4 Recommended Tool List



Section 5: Site Preparation 5.1 5.2 5.3



Excavation Layout Excavation in Soil Excavation in Rock

Section 6: Construction



6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11

Bridge Terminology Guide Foundation Tier Construction Tower Construction Anchor Construction & Cable Installation Cable Sag Setting Cable Clamp Installation Cable Care Bridge Approach Construction Wood Deck Installation Connecting Deck to Approach Fencing Installation

Section 7: Bridge Completion

SECTION 1: CONSTRUCTION OVERVIEW Preparation

• Total time required: variable, 2 weeks to several months

> Material Collection and Excavation

Responsibilities Community Labor River rock Implementing Agency Supervision - 5 days Sand, gravel and blocks Construction materials Cement, rebar and misc. items



Construction • Total time required: variable, 2 to 4 months

> Foundation Tiers - 2 to 4 weeks

Responsibilities Community Labor Implementing Agency Supervision - 5 days Masons

Volume 3: Suspended

Part 3 - Construction Guide



4

> Tower Construction and Saddle Installation - 5 days Responsibilities Community Labor Implementing Agency Supervision - 5 days Masons



> Cable Installation and Anchor Pour- 3 to 5 days (add 4 days for concrete curing time) Responsibilities

Community Labor Implementing Agency Supervision - 3 days Masons

> Cable Sag Set - 2 days Responsibilities Community Labor Implementing Agency Supervision - 2 days Masons



Volume 3: Suspended

Part 3 - Construction Guide



5

> Approach Construction - 1 to 4 weeks

Responsibilities Community Labor Implementing Agency Supervision - 3 days



> Deck and Fencing Installation - 3 to 5 days

Responsibilities Community Labor Implementing Agency Supervision - 2 days



> Bridge Opening Ceremony - 1 day

Responsibilities Community Coordination Implementing Agency Attendance

Volume 3: Suspended

Part 3 - Construction Guide



6

SECTION 2: SAFETY 2.1

Travel Member Responsibilities

2.2

B2P Health and Safety Plan

2.3

Safety in Project Planning

All team members and community members working on site must abide by the B2P Health and Safety Plan, and actively engage with the Safety Manager, aligning with all safety plans and protocols.

In conjunction with our partners and industry professionals, Bridges to Prosperity developed the B2P Health and Safety Plan to address the hazards that may be encountered on a bridge site. In many of the countries where B2P operates, safety standards that are commonplace in many western countries are largely absent or, at best, casually enforced. National organizations focused on safety in many countries, like OSHA in the United States, may lack presence in rural areas or may not exist at all. B2P values the health and well-being of all personnel on bridges sites, both local community members and visiting volunteers, and expects the Health and Safety Plan to be applied comprehensively on site. This often means that foreign volunteers have the opportunity to share their experiences in work site safety with local laborers to ensure a safer workplace for all. This exchange of ideas in safety culture awareness is a keystone in the “Build to Educate” component of B2P’s mission. Bridges to Prosperity has developed the B2P Health and Safety Program with the aim to develop the same culture of safety that is paramount to success in the construction industry. Daily actions, like the use of personal protective equipment or fall protection, are critical to safety on any work site, however, developing a robust and comprehensive site specific safety plan is the most important aspect of ensuring a culture of safety on a bridge site. Safety must be considered at multiple levels: Whole project level: What actions contribute to a culture of safety over the duration of the entire project? Planning for project safety should take place before the ground breaking of a project and should encompass a broad perspective of a culture of safety. Considerations may include: the location of water, latrines and other sanitation needs for workers, the location of the nearest emergency medical attention, relations with the local community especially regarding safety concerns, resources that may be available for safety training for workers, etc. Daily work level: What are the work objectives for a specific day, and how does a team minimize risks and hazards while completing those work objectives? This type of planning should be done every day with the workers who will be on site that day. The plan should consider the specific tasks planned for the day, recognize any potential hazards and determine what safety measures need to be taken. Individual task level: What actions can be taken while preforming a specific task to ensure that the work is done in the most safe manner possible? This type of planning should be done on a constant basis by each worker, considering how they are going to do each task in a safe manner and how that task relates to the Daily Work Plan that was devised at the beginning of the day.

Volume 3: Suspended

Part 3 - Construction Guide



7

2.4

ON-SITE SAFETY Safety System This safety system was developed to better understand the aspects of safety. There are six different elements to this Safety System: 1. Commitment 2. Communication 3. Planning 4. Education 5. Evaluate/Modify 6. Reinforcement Each of these will be further explained in the following sections. Refer to the B2P Safety Training PowerPoint presentation for additional information before completing the B2P Safety Training Quiz, found at bridgestoprosperity.org/Resources. Commitment Safety is a function of leadership. As a result, safety must start from the top of an organization and be consistent throughout. Expectations need to be set and met by all people on the team without exception. Communication Communication and working safely go hand in hand; workers that are uninformed have the highest potential for injury. The Safety Manager on site needs to ensure that everyone on site knows and accepts the expectations. This includes both local community members and visiting volunteers. Safety briefings and discussions must be thoroughly communicated in the local language to any community members involved in that task. The Safety Manager is responsible for ensuring that a translator conveys the necessary information and answers any questions that come up. Note: A language barrier should never be grounds for exclusion of community members in a construction task. Ultimately, it is their bridge and they should be able to help in any task. The Project Manager and Safety Manager must coordinate with a translator as necessary.

Volume 3: Suspended

Part 3 - Construction Guide



8

Planning Thorough planning is critical to achieving two goals of a robust safety plan: 1) eliminating incidents and problems that can create disruptions in work, and 2) increasing efficiency by creating a safe work environment. B2P’s standard planning forms make this goal easily achievable. Bridges to Prosperity has used industry standard material and the assistance of safety professionals to ensure our Safety Program achieves the same culture of safety that is a keystone to success in the construction industry. Project Planning forms All of the following forms can be found under the Resources section of the website: bridgestoprosperity.org/resources/technical-resources/

FORM NAME

REQUIRED ON SITE

REQUIRED SUBMISSION TO B2P

Daily Work Plan Yes Daily Site Inspection Yes Excavation Inspection Yes Fall Protection Inspection Yes Work Area Hazards Yes End of Day Review Yes Incident Report Yes *when applicable meaning when that type of work is included in the Daily Work Plan.

Yes Not Required Not Required Yes Not Required Not Required Yes

FREQUENCY Daily Daily Daily (when applicable) Daily (when applicable) Daily Daily As Needed

Education On most projects, each person brings a different level of safety training and experience. It is essential that everyone on the work site can effectively identify hazards and knows the best measures to protect themselves. A bridge project is an opportunity for safety-educated workers to teach those who have less knowledge and experience staying safe on a work site. This includes both local community members and visiting volunteers. Safety managers should organize all training sessions necessary to ensure that all personnel thoroughly understand the hazards associated with all tasks and how those hazards can be mitigated. No worker’s health and safety is ever more valuable than another worker’s. Safety standards are to be applied equally to all personnel working on site. It is possible that language barriers and cultural differences will require that more time is spent on training.

Volume 3: Suspended

Part 3 - Construction Guide



9

Evaluate and Modify It is important to continually evaluate both conditions and actions on a work site since they are both always changing. It is important that everyone on site is paying attention to any changes or modifications; passers by who may be unfamiliar with the safety expectations when they join in to help; something that just doesn’t look right; and near hits or misses. If any of these are seen, it is important that everyone stops to discuss them as a team. Reinforcement Individuals frequently choose safe behavior as a result of either positive activators or consequences. It is important that all workers receive proper feedback from both peers and the Safety Manager. Safety Culture Bridges to Prosperity’s goal is to develop a safety culture as strong as the safety culture of our partners on their projects in developed countries. A strong safety culture is a product of shared safety values, attitudes, goals and practices where commitment, communication, and planning occurs on a daily basis. It is important that all personnel on B2P bridge sites support one another in safe work practices. Furthermore, the Safety Manager on site must share any feedback regarding the safety on site and ways that the safety culture can be improved. Near Misses A near miss is an event that did not result in injury, illness or damage but had the potential to. Near misses are important because they can teach a great deal without any injuries, illnesses or damage occurring. Many people do not report near misses for a fear of punishment or lack of understanding of their importance. The information gathered from near misses can be used to modify bridge building procedures in order to avoid similar dangerous situations in the future. B2P’s goal is to have a system where reporting near misses can be done effectively and efficiently. If these are not reported, someone else could be injured unnecessarily.

Volume 3: Suspended

Part 3 - Construction Guide



10

Personal Protective Equipment (PPE) The goal of a safety program is to eliminate many of the hazards through engineering and safe work practices. However, not all hazards can be eliminated so personal protective equipment is still necessary. Personal protective equipment or PPE is worn to act as the last line of defense against injury or illness. There are many different kinds of PPE depending on the work and the equipment involved. Hard Hats Hard hats are most important when there is a possibility of hitting your head on low hanging objects or when there is the possibility of falling objects. Even if these hazards are not present, it is still a good idea to wear a hard hat when possible. Safety Glasses Safety glasses are required when any of the following are present: • Dust and other flying particles • Corrosive gases, vapors, and liquids • Molten metal that may splash • Intense light from welding and lasers Face Shield The face shield provides more complete protection of the face than safety glasses. It is to be worn when there is significant exposure to dusts, splashes or sprays of hazardous liquids. The face shield does not provide much protection from impacts, though. It is to be worn with safety glasses underneath. Face shields must be worn when cutting rebar, cables or during other activities involving the grinder.

Hearing Protection There are many different types of hearing protection. These include ear plugs, canal caps and ear muffs. The rule of thumb is that if you have to speak loudly with a colleague, from two feet away, you need to wear hearing protection.

Volume 3: Suspended

Part 3 - Construction Guide



11

Work Boots Work boots should be worn at all times while on bridge sites but are most important when heavy falling objects, sharp objects, hot surfaces and/or wet surfaces are present. Work boots are typically made of leather and provide ankle support. Some work boots have a steel reinforced toe as well but this is not a requirement of B2P.

Hand Protection Hand protection, typically gloves, can protect hands from cuts, crushing, abrasions, hot and cold temperatures, and chemicals. There are different types of gloves for different types of applications. Leather, fabric, coated fabric and rubber are some of the more common ones. Leather gloves are best for protecting against cuts, burns and heat. Fabric and coated fabric gloves are best for protecting against dirt and abrasion. Rubber gloves are best at protecting against chemical burns.

Hand and Power Tool Safety Tools are essential for all Bridges to Prosperity projects. While tools are very helpful, and in some cases essential, they can also be very dangerous. This section will discuss the hazards associated with tools and ways to prevent possible hazards. General Hand Tool Safety Basic hand tools are used on a daily basis on all work sites. When working side by side with local community members, a vast array of tools in various states of repair are likely to surface. It is imperative to site safety that the tools being used by both visiting volunteers and local community members are inspected to ensure that they are in proper working condition and will not create unnecessary hazards.

Volume 3: Suspended

Part 3 - Construction Guide



12

Come Along Safety Come alongs, also known as hand winches, cable pullers, or cable hoists, are used for cable placement and sag setting on all Bridges to Prosperity projects. These are two of the most critical steps in the construction process and are potentially some of the more dangerous. Special care needs to be taken in the selection and use of a come along. Any failure can lead to a cable slip, which is extremely dangerous. A loose cable can whip out of control and cause significant injury.

Some General Rules for Using a Come Along: • ALWAYS double-check the calculations for the calculated load that is being pulled • Ensure that ALL devices being used are capable of carrying the load force, including the anchor points, and any other straps or fastening devices that may be used to carry the load • ALWAYS make sure the device is well maintained and the safety latch is working properly • ALWAYS check the cable and chain for damage (i.e. corrosion, failed links, etc.) • ALWAYS use appropriate end clamps and connections • ALWAYS use the proper personal protective equipment when operating a come along • DO NOT use if parts are damaged • DO NOT exceed the rated capacity of the come along • DO NOT use a cheater bar • NEVER straddle the tool • Keep your body out of harm’s way SAFETY DURING CABLE TENSIONING

Volume 3: Suspended

Part 3 - Construction Guide



13

Power Tools As the size and complexity of B2P’s bridges grow, the use of power tools on site is becoming more prevalent. This necessitates that extra care is taken in not only using those power tools, but in making sure that all personnel using those tools are sufficiently trained and aware of the safety requirements of each device. For many community members, it will be their first exposure to using power tools. Naturally, they are eager to help and learn new construction methods, but they may be unfamiliar with the hazards of such tools. For community members using power tools, patient, clear instruction and close supervision are absolutely required. General rules for power tool safety: • Disconnect tools when not in use, before servicing, and before cleaning or changing accessories on the tool • Try to secure work with clamps or vices to free both hands to operate the tool • Always keep tools sharp and clean • Consider what you are wearing when operating power tools: loose clothing and jewelry can get caught in moving parts • Remove damaged electric tools and mark them “DO NOT USE” in both English and the local language, and communicate the meaning of this to all workers. It is also a good idea to keep the damaged tool separate from the operational tools. • DO NOT hold the switch button while carrying a plugged in power tool Regarding corded power tools: • Keep cords and hoses away from heat, oil, and sharp edges • When possible, use tools that are properly grounded and that are double insulated • DO NOT carry portable tools by the cord • DO NOT hoist or lower power tools by their electrical cords • DO NOT yank a cord or hose to disconnect it • Make sure the cord is not in the way of the work Best practices: • Operate within design limits • Use gloves, safety glasses, and safety shoes • Store tools in a dry place • Don’t use in wet locations unless tool is approved for use in those conditions • Keep work areas well lit • Ensure that cords don’t present a tripping hazard

Volume 3: Suspended

Part 3 - Construction Guide



14

Fall Protection It takes a person approximately 1/3 of a second to become aware that they are falling. It takes an additional 1/3 of a second for the body to react. In that 2/3 of a second, the human body can fall up to seven feet! Fall protection is required for any person working off the ground. Overview Fall prevention is a series of reasonable steps taken to eliminate or control the potential effects of an unintentional fall while accessing or working at heights. This is applicable when constructing the deck and when working on the towers for a suspension project. Best way to control fall exposures: • Always try to eliminate the hazard • Select appropriate fall protection systems • Properly construct and install the systems • Train workers in the proper selection, use and maintenance of fall protection systems • Supervise everyone on site wearing fall protection Types of fall protection Fall protection is necessary for anyone that is working 6 feet (~2m) above the ground or higher. There are different types of fall protection that can be used when working on a surface that meets this criteria. Harnesses Harnesses are devices that are worn over your clothes and they are designed to catch and support you when you fall. There is a main ring or the “D-ring”on the harness that when worn properly, is located on your back between your shoulder blades. This ring is where you connect your lanyard or retractable and is what catches you if you fall.

D-Ring

General fitting rules: • Be able to touch your D-ring with your thumb • Maximum of 4 (flat) fingers of slack in the leg straps, fitted as high as is comfortable • Chest strap should be across the breast bone • Have someone else check the harness for twists in the straps Harnesses must be inspected before each use. Bridges to Prosperity has an inspection form that can be used to help in this process. If a harness is identified as deficient, it must be labeled as such and

Volume 3: Suspended

Part 3 - Construction Guide



15

taken out of service immediately. Lanyards The simplest of connections from a harness to an anchorage point, lanyards, come in many different styles and lengths. It is important that the lanyard being used will in fact provide the desired protection. For example, if an individual is working 6 feet above the ground and they are using a 6 foot (~2m) lanyard, they will likely hit the ground before the lanyard is engaged. With a 6 ft lanyard, a minimum of 18.5 feet (5.6m) of clearance is needed between the individual and the ground. Self-Retracting Lifeline A self-retracting lifeline (also known as retractable or yo-yo) is also used to connect a harness to an anchorage point. The added benefit of these is that they function similarly to a seat belt. If you pull slowly, it will release slack, but if you pull quickly it locks up, minimizing free-fall distance to a couple of feet. These work best in vertical applications. Do not connect two retractables in a series. They are not designed for this application and may not function properly if used as such. Also, if used in a more horizontal application, although the retractable will lock up, it is likely that the individual will swing. This is called a “swing fall” and it can be very dangerous if there are nearby obstacles that the individual might swing into. Keep this in mind when finding or designing an anchorage point. Anchorage Points Equally as important as the harness and the connection is the anchorage point, or the point from which you are tying off. Keep in mind that an anchorage point must be able to support 5,000 lb (2300 kg) per person or twice the intended load when using a horizontal lifeline. If a retractable is being used, the bearing capacity of the anchorage point can be reduced to 3,000 lb (1400 kg) per person. It is always best to tie off to a point that is at or above the D-ring’s height. Also, make sure that the anchorage point is convenient for the individual. In the picture to the right, note that the workers are tied off to a cable that is set higher than the main cables to serve only as a tie off point. Rescue Plan With fall protection, it is important to not only protect against falling but to also to have a plan of how to safely rescue the individual from their position after the fall. It is likely that an individual that just fell will not be able to pull themselves up. Also, when the individual is suspended in the harness, it does not take long before the straps will start cutting off the circulation to legs (though, some harnesses have straps that the individual can put their feet into to help take pressure off the leg straps). If a plan is not made ahead of time, there may not be enough time to rescue the person before they go into shock.

Volume 3: Suspended

Part 3 - Construction Guide



16

Also, it may take more than one person to lift the fallen individual, so plan accordingly. Trenching and Excavation Safety Excavations and trenches pose another major safety concern on bridge sites. It is essential to know the in-situ soil and rock conditions when planning excavation and trenching activities. Background An excavation is any man made cut, cavity, trench, or depression in an earth surface, formed by earth removal. A trench is a more specific type of excavation. A trench is an excavation that is narrow in relation to its length below the surface of the ground. In general, the depth is greater than the width, but the overall width of a trench is not greater than 15 ft (4.6 m). Rock and Soil Properties When making an excavation or trench, it is important to know the soil properties to ensure that the excavation is safe to work in. There are three classifications of soil, as well as stable rock. The type of soil is what dictates the allowable slopes of the excavation (see the following types below). Stable Rock Stable rock can be best defined as a natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed. While this does produce the most stable type of excavation and is best for foundations, it is not very common. Type A Soil A type A soil is a cohesive soil with an unconfined compressive strength of 1.5 ton per square foot or greater. Examples a cohesive soil are clay, silty clay, sandy clay and clay loam. However, a soil cannot be classified as a type A soil if the soil is fissured or the soil is subject to heavy vibration from traffic or equipment. It can also be denied type A soil classification if it has been previously disturbed. Type B Soil A type B soil is a cohesive soil with an unconfined compressive strength of between 0.5 and 1.5 ton per square foot. They can also be granular, non-cohesive soils such as angular gravel (crushed rock), silt, silty loam and sandy loam. Previously disturbed soils can also qualify as type B soil, as well as type A soils that have been fissured or subject to vibration. Finally, it can be dry rock that is not stable. Type C Soil Type C soil consists has a compressive strength of 0.5 ton per square foot or less. It also can include granular soils including gravel, sand, and loamy sand. Submerged soil or rock from which water is freely seeping is also classified as a type C soil.

Volume 3: Suspended

Part 3 - Construction Guide



17

Soil Test and Classification There are a few different low tech field tests that can be performed to properly identify soil type. These methods include the thumb test, plasticity, and a pocket penetrometer. Each of these is a simple way to classify the soil relatively accurately in very little time. It is important to note that if the test results are not clear, it is always better to assume a less stable soil. The Thumb Test (ASTM test designation D 2488) For this test, one must retrieve a large clump of undisturbed soil. Next the individual must attempt to penetrate the soil with the tip of their thumb. A type A soil can only be penetrated with a great force. Alternatively, a class B soil will penetrate to the full length of the thumb nail and a type C can be penetrated several inches with ease. However, given the imprecision of this test, it is best to classify conservatively. Plasticity Test For this test, collect a small sample of soil and add water until it is moist. Roll the soil into a ball, and then into a 1/8” diameter thread. If this can be done, hold the sample by an end. If it remains suspended without tearing, the soil is cohesive. Pocket Penetrometer A handheld device that is used to measure the bearing capacity of the soil at a given location. It is best to read a users manual for the specific penetrometer that is being used, but the following can be used as a generic procedure for most penetrometers. First, collect a sample of undisturbed soil. The easiest way to get this is to dig a hole and use the penetrometer on the shear face of the small excavation. Next, on the penetrometer, move the ring to the lowest reading on the scale, which should correspond to the lower edge of the instrument handle. Slowly push the piston into the soil up to the groove that should be located 1/4” away from the end of the instrument. Once the end has penetrated the soil up to that point, pull the instrument away from the soil and read the value marked by the location of the ring. This value will give you the compressive strength of your soil in tons per square foot (tsf) or kg per square centimeter (kg/cm^2).

Volume 3: Suspended

Part 3 - Construction Guide



18

Allowable Excavation for Type A and B Soils

Allowable excavations per OSHA Type A Soil

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Volume 3: Suspended

Part 3 - Construction Guide



19



Type B and C Soils

Volume 3: Suspended

Part 3 - Construction Guide



20

SECTION 3: QUALITY CONTROL 3.1

QUALITY CONTROL OVERVIEW As with any construction project, there must be an aspect of quality control. It is imperative that these types of international projects be built to the same standards as projects built in the U.S. or other developed countries. This section will assist you in making sure that all construction methods are followed properly. This section is not intended to be a hindrance, but rather an aid for individuals that lack experience working in remote areas.

3.2

QUALITY CONTROL REQUIREMENTS The requirements of quality control while working on a Bridges to Prosperity project are specified below. If working completely independent of B2P, the following items are still highly recommended. Requirements 1. Photo Inventory and Submission 2. Quality Control forms 3. As-Built Reports

Volume 3: Suspended

Part 3 - Construction Guide



21

Photo Inventory and Submission The following is a list of photos that MUST be taken during construction. These photos are to ensure that each step of the process was properly executed and may be referenced when performing inspections. Upload to the appropriate Flickr folder, named: QC_[Name of bridge]. If you have questions about where or how to submit photos, please contact B2P at [email protected].

A. Site • A1- River profile (looking up or down stream) • A2- Pulled centerline with indication of tower locations B. Excavations • B1- Anchor excavation depth • B2- Foundation depth C. Foundation and Tiers • C1- Foundation wall construction • C2- Complete foundation walls • C3 - Foundation after it is filled • C4 - Filling voids with grout D. Towers • D1- Rebar installation in tower • D2- Saddle placement and alignment • D3- Distance from walkway to handrail • D4- Walkway hump E. Anchors • E1- Completed rebar cage • E2- Cross-section of cable with ruler/tape measure • E3- Cable position in excavation taken from centerline • E4- Completed anchor

Volume 3: Suspended

Left

Right

Part 3 - Construction Guide

F. Sag Setting • F1- Handrail and walkway cables aligned/even • F2- Clamp spacing • F3- Torque technique used • F4- Representative photo of clamped cable • F5- Filling tubes with grout (adjustable side) • F6- Tar on cables that will be underground G. Approaches • G1- Thickness of approach walls • G2- Approach filled • G3- Completed approach H. Suspenders, Decking and Fencing • H1- Decking installation process (proper PPE) • H2- Finished deck • H3- Suspender connection to crossbeam • H4- Suspended connection to handrail • H5- Fence installed I. Completed Bridge • • •

Left

Right

I1- Taken from bridge centerline I2- From right abutment I3- From upstream or downstream



22

Example Suspended QC Photo Submission The following are example QC photos with a brief description of what should be shown in the photo.

A1. River profile: • Signs of erosion • Bends in the river • Profile of the river and surrounding area • Gorge vs. floodplain • Current water level • Existing infrastructure that may interfere

A2. Pulled centerline with indication of tower locations: • Visual of the bridge centerline • Reference for survey • Identify potential conflicts

Volume 3: Suspended

Part 3 - Construction Guide



23

B1. Complete anchor excavation depth: • Excavations depth per drawings • Proper benching or sloping of excavations • Soil type identification

B2. Complete foundation excavation depth: • Excavations depth per drawings • Proper benching or sloping of excavations • Soil type identification

Volume 3: Suspended

Part 3 - Construction Guide



24

C1. Foundation wall construction: • Walls constructed per manual recommendation • Example: stone oriented horizontally rather than vertically • Proper wall thickness

C2. Complete foundation walls: • Walls constructed per manual recommendation • Example: stone oriented horizontally rather than vertically • Proper wall thickness

C3. Foundation after it is filled: • Rock/stone fill • Completion of tier

C4. Pouring grout in voids: • Is the granular fill grouted per manual? • Correct consistency for the grout • Top of tier capped

Volume 3: Suspended

Part 3 - Construction Guide



25

D1. Rebar installation in tower: • Tower reinforcement bar per design drawings • Correct size and quantity • Placement within base

D2. Saddle placement and alignment: • Saddles installed per design drawings (in Volume 3.3 Construction Manual) • Parallel to bridge centerline • Identify potential conflicts for cable due to shortened height or differing angle

D3. Distance from walkway to handrail saddle • Built per design drawings (in Volume 3.3 Construction Manual) • Correct distance from handrail to walkway saddle

D4. Walkway hump: • Walkway hump built • Walkway saddles installed parallel to final lay of cable (installation optional)

Volume 3: Suspended

Part 3 - Construction Guide



26

E1. Completed rebar cage • Correct size and number of bars in rebar cage • Tied per design drawings

E2. Cross section of cable with tape measure: • Validation of wire rope/strand type • Diameter

E3. Cable positions in anchor for alignment • Cables are spaced along the anchor per the design drawings • Rebar cage properly positioned • Cable tied/positioned in parallel to the loaded position

E4. Completed anchor: • Rebar completely covered • Concrete quality • Cable paths clear of rocks, soil, and other debris

Volume 3: Suspended

Part 3 - Construction Guide



27

F1. Walkway and handrail cables level with one another • T-square is vertical (or show equivalent method) • Cables sit at equal height relative to one another

F2. Clamp spacing: • Proper clamp spacing for the given diameter of the cable

F3. Torque technique used • Demonstrate torque technique • Appropriate size wrench/ tool to achieve required torque F4. Representative photo of clamped cable: • Proper number of clamps • Cable showing 20% reduction when clamped

F5. Filling tubes with grout (not pictured): • Showing that tubes were filled • Proper grout consistency

F6. Tar on cable where it will be underground: • Cable coated in tar where in contact with the soil

Volume 3: Suspended

Part 3 - Construction Guide



28

G1. Thickness of approach walls • Correct size and number of bars in rebar cage • Tied per design drawings

G2. Approach wall connecting abutment to anchor: • Approach walls that connect the tiers/foundation to the anchor per standard drawings

G3. Approach filled • Ramp filled with rocks and granular materials • No soil backfill (in particular organics or soils with clay content)

G4. Completed approach: • Ramp constructed per design drawings, • Sloped access for bikes/motos/livestock • Capped surface complete

Volume 3: Suspended

Part 3 - Construction Guide



29

H1. Decking installation process (proper PPE) • Decking process per Volume 3.3 directions • All workers tied off • Check for irregularities in fall protection • Verify safety line above deck or handrail cable

H2. Finished deck: • Decking installed per design drawings

H3. Suspender connection at crossbeam: • Crossbeam connection per design drawings and volume 3.3 • Diameter of drilled crossbeam hole allows movement of suspender

H4. Suspender connection at handrail: • Proper suspender connection at the handrail • Tail of the suspender outside of walkway area H5. Completed bridge: • Fencing properly installed • Connected at each suspender • Wrapped over handrail.

Volume 3: Suspended

Part 3 - Construction Guide



30

I1. Completed bridge from bridge centerline • Decking process per Volume 3.3 instructions • All workers tied off • Check for Irregularities in fall protection • Verify safety line above deck or handrail cable

I2. Completed bridge from abutment: • Crossbeam connection per design drawings and Volume 3.3 instructions • Diameter of drilled crossbeam hole allow for movement of suspender

I3. Completed bridge from upstream or downstream: • Fencing properly installed • Connected at each suspender • Wrapped over handrail

Volume 3: Suspended

Part 3 - Construction Guide



31

3.2.2 Quality Control Forms At the end of each step of construction in Section 6, there is a Quality Control Checklist that needs to be filled out and submitted to B2P.

3.2.3 As-Built Report Requirements As-built reports are markups done to the construction drawings that better represent how something was actually built. During the construction of a bridge, there are likely components that will not be built to the exact specifications. However small these differences may be, it is important to document them. Each dimension in the drawings needs to either have a check mark next to it or have an updated value (preferably in red ink). These then need to be scanned at the end of the project and submitted to B2P.

Volume 3: Suspended

Part 3 - Construction Guide



32

3.3

MATERIAL QUALITY CONTROL The quality of a bridge project is completely dependent on the materials used. During the project, it is important to use the best materials available. This section should be used as an aid in sourcing materials for construction. If the materials used are in question, it is best to consult experienced personnel before using them.

Concrete

The intention of this section is to serve as a guideline for standard and replicable concrete mixing techniques for use on all projects. It is to be used as an outline and does not attempt to cover all situations encountered in the field. This guideline is to be used in association with the Concrete QC Checklist which will keep track of the quality of concrete on the job and must be submitted upon project completion. Quality Control Person Assign one person to oversee concrete proportioning and mixing operations. They will be considered the Quality Control (QC) person for concrete operations. This individual should be present during all concrete proportioning and mixing and should be experienced in concrete and capable of making decisions in the field. Note that if for some reason, this person cannot be present throughout the duration of the project, the head mason for the project, in most cases a local, should be trained and held responsible for concrete mixed on site without the QC person. Materials Check the availability and quality of required materials. Locate the source for cement, sand, gravel and water on the job site or elsewhere if necessary. Ensure the following: • Cement should be fresh (no older than 60 days) and from a reliable source • Sand and gravel should be clean and free of debris (sticks, leaves, trash, etc.) • Sand should be coarse, not round or shiny • Sand should not contain silt or clay particles • Water should be clean and transparent • Gravel should be no larger than 5cm • Gravel should be relatively round yet jagged (note: round refers to the overall shape and not the surface) Also, note that there are different types of cement and varying levels of quality. Ensure that the cement being used is of good quality and is the desired type.

Volume 3: Suspended

Part 3 - Construction Guide



33

Mix Ratio For all B2P projects, a 1:2:3 volumetric mix ratio is recommended. This means that one bucket of cement is mixed with two buckets of sand and three of gravel (Note: the size of the buckets does not matter as long as it is consistent). Below is a table representing the amount of cement, sand, and gravel needed for 1 cubic meter of concrete. Note that the below table is more useful in estimating total materials needed rather than for use when mixing concrete. Materials Needed for 1 Cubic Meter of Concrete Using a 1:2:3 Mix Design Cement ( m 3 ) 0.25 (8 x 42 kg bags)

Sand ( m 3 ) 0.5

Gravel ( m 3 ) 0.75

Yield ( m 3 ) 1.0*

*Note that it is assumed that there is a 33% reduction from the summation of the volumes of the components to the volume of concrete produced. The water amount will likely vary from site to site, based on the characteristics of the aggregates. As a starting value for the volume of water, we recommended adding the water necessary for a minimum slump and then adding water in small amounts until the desired consistency is reached. For a 1 - 2 inch (2.5cm - 5cm) slump with 5cm gravel, the recommended water is 0.15 cubic meters per cubic meter of concrete*. This means that for the diagram below, it is recommended to start with about one half of a bucket of water and then continue to add water until the desired consistency is met. A slump test is very useful for this application and is covered in a following section. *Design and Control of Concrete Mixes,14th edition  

Cement  

Volume 3: Suspended

Sand  

Gravel  

Part 3 - Construction Guide

Concrete  



34

Concrete Mixing Methods The method used to mix the concrete can have significant impact on the final strength of concrete produced. We recommend the use of a mechanical mixer whenever possible, as it usually produces much stronger concrete in comparison to hand mixing.

Recommended Materials • Shovels • Gloves • Buckets • Cement • Sand • Gravel • Flat clean working area • Water

• Safety glasses

When using a mechanical mixer, it is recommended that some of the water is added first. The volume of water needed will be 60% of the volume of cement added (i.e. 0.6 buckets of water for 1 bucket of cement). Following that, all dry materials should be added. Let the materials become well mixed and slowly add water until the desired consistency is reached. Add water slowly for the first batch and for subsequent batches; water can be added more quickly with a better idea of how much will be required. When the use of a portable mixer is not feasible, a manual method of concrete mixing is required. In order to ensure material strength properties assumed in the design, it is important to use only clean and fresh materials and mix them using the “sifting method.” Before starting, pour a thin concrete pad where the concrete mixing will take place. This will limit the amount of unwanted constituents in the mix (i.e. soil, grass, sticks,etc.) and will allow less water to escape the mix. The sifting method requires the materials to be added in sifts. Mix the dry gravel and sand first. Once that is well mixed, add the cement and gently mix the pile so no cement is lost (cement is very light). Using shovels, mix the dry components thoroughly. Do so by shoveling into a single pile, then moving the pile twice (back and forth). After the dry materials are well mixed, add water using the same method stated above. During this process, continue moving the pile to ensure uniformity. The sifting water method is superior to the “volcano method” or cone method that is commonly used. The puddle of water in the middle of the cone shape does not produce an even and consistent product, as when water is mixed slowly and evenly into the mixture. A slump test is highly recommended for the first batch to ensure the mix design is adequate. More details on how to preform the slump test are included later in this section, but a slump of 3-4 inches (7.5cm -10cm) is recommended. Placing Concrete Concrete should always be placed within one hour of mixing. If this time limit is exceeded, the concrete should be discarded. However, if working on a hot day, this time could be significantly reduced.

Volume 3: Suspended

Part 3 - Construction Guide



35

Curing Fresh concrete will crack when it is allowed to dry rapidly. Thus, curing the concrete is essential. After the concrete is placed, covering the concrete will help reduce the amount of moisture lost due to evaporation and to help ensure consistent hydration. Wet burlap sacks or plastic sheeting works best, but anything that helps reduce water loss is acceptable. Moistening the empty cement bags and covering the fresh concrete with them is another good option for curing. Whichever is used, add water each day to the surface of the concrete to better hydrate the concrete. When pouring the anchor, allow four days of cure time before loading cables with decking. Although the anchor will not be nearly at the 28-day strength, the crushing strength of the concrete need only be approximately 250psi before loading. Admixtures - Accelerators Concrete accelerants can be used to increase the speed of strength development. There are different types of accelerants. Obtain all necessary product specifications for the application and dosage required. If accelerant is used, remember: • Read all available manufacturer literature and ensure proper dosage • Reduce the initial amount of water added to the mix per the manufacturer’s instructions (approximately 25% is typical) • The accelerant will act as a plasticizer so it will reduce the amount of water needed to reach the desired consistency When using an accelerant, it is recommended to pour a test cylinder or equivalent shape at the same time as placing the concrete. When the recommended time has elapsed, take that cylinder and break it. This should give some indication of the strength of the concrete that has been poured. For this to be effective, make sure the cylinder has been cured in similar circumstances as the placed concrete. Also note that many accelerants contain calcium chloride. There is significant data that indicates that these types of accelerants increase drying shrinkage, increase potential for reinforcement corrosion, and increase potential for scaling. If the accelerant available contains calcium chloride, it is recommend that a professional engineer be consulted to determine how to proceed. The following example uses Sika Rapid-1, a non-chloride containing accelerant. Example: The following is an example of the type of product specifications that may be found on a container of accelerant or on the manufacturers website. If 3 cubic meters of concrete is needed for the anchor and the anchor needs to be loaded as soon as possible, how much Sika accelerant is needed? 1. Identify how many kilograms of cement is needed for the 3 cubic meters of concrete. In this case, 8-42 kg bags per cubic meter so 8*42*3=1008 kg. 2. Look at the manufacturers recommendation for milliliters needed per kg of cement. In this case it is 520-1950 mL per 100 kg of cement Lets say 1000 mL per 100 kg. 3. Take 1,008kgs of cement *(1,000 mL /100 kg cement). The result is 5,242 mL min. and 19,660 mL max. Note that this is for 8 bags and a more useful number would be per bag of cement. Take these values divided by 24 bags to get 220mL min. and 820 mL max. 4. Let’s say 500 mL per 42 kg bag of cement, and we will need 12 liters total. For this, cut the top off of a 1 liter bottle of water and mark the 500mL line. Use this for adding to the mixes.

Volume 3: Suspended

Part 3 - Construction Guide



36

Grout and Mortar Mixes Grout and mortar mixes are required at various locations on the bridge. Mortar is used as part of masonry walls and grout is used in the tubes at the anchor locations. Mortar is often made from cement and sand (roughly 1:4, with water added until workable) and does not contain large aggregates. Grout mixes are typically from a bag and do not contain any aggregate.

Slump Test If there is a standard slump cone available on site, take one slump test per batch of concrete made. A slump test is used to help verify the workability and mix proportioning of a single batch of concrete. It is also useful to determine consistency between multiple batches of the same mix of concrete. In order to perform the test you will need some basic tools listed below. The slump cone needs to be exactly as specified, but the scoop, slump board and tamping rod can be whatever is available on site.



Tools Required • Slump cone - 20cm (8”) base diameter. x 10cm (4”) top diameter. x 30cm (12”) tall • Slump board - smooth flat surface • Concrete scoop • Tamping rod - ~1.58cm diameter (5/8”) x 40-50cm (16”-18”) long, smooth steel rod • Tape measure

The slump for any batch of concrete (excluding grout mixes) should be from 3-4in. (7.5-10cm) and be no more than 11cm (5in). If a batch of concrete exceeds this amount, either discard the batch or use it on a non-critical part of the bridge (listed on the QC checklist). Also, the use of concrete admixtures, such as liquid accelerants, can affect the slump of the concrete. If an admixture is used, refer to the manufacturer’s data to verify if and how the slump will be affected. Recommended slumps for various types of construction are shown in the table to the right.

Volume 3: Suspended

Part 3 - Construction Guide



37

Slump Test - Procedure Step 1: Moisten the slump cone, tamping rod, scoop and slump board so that they are wet to the touch. Step 2: Place the slump cone (large side down) on the slump board and secure it in place by standing on the fins at the base of the cone. Step 3: Fill the cone a third of the way with concrete (to a height of 2-5/8”). Then, use the tamping rod to consolidate the concrete in the cone by use of an up and down motion, 25 times. Fill the cone another third of the way, and repeat the tamping motion 25 times while just penetrating the first layer. Fill the cone the remainder of the way, and repeat tamping 25 times, just barely penetrating the second layer. Use the rod to smooth off and remove any excess concrete from the top of the cone. Step 4: Slowly pull the cone upwards (it should take about 5 seconds to completely remove the cone). Then, turn the cone over (small side down) and measure the distance between the top of the cone, and the center of the top of the “slumped” concrete. This measurement is your slump. Step 5: Compare results to expected values.

Volume 3: Suspended

Part 3 - Construction Guide



38

Compressive Test We encourage making concrete cylinders that can be used for strength testing. The results will be useful in developing future mix proportioning guidelines and in bridge evaluations. Note that grout mixes use a different testing method that is not outlined here. Tools Required • Plastic cylinder molds - 10cm (4”) diameter. x 20cm (8”) tall • Smooth flat surface • Concrete Scoop • Tamping rod - ~1.58cm diameter (5/8”) x 40-50cm (16”-18”) long, smooth steel rod with rounded end

Procedure for Casting and Storing Concrete Cylinders Step 1 Label the molds with the proportion of the mix, date, and final location of the concrete. Step 2 Place the molds to be filled on a flat, level surface. Fill the molds in three equal layers, rodding each layer 25 times with the tamping rod (when rodding the second and third layers, the rod should just penetrate the previous layer). After the cylinder molds are filled, tap the outside to help further eliminate voids in the mold. Strike off the top of the cylinder using any straight edge you have, and put the cap on. Step 3 Carefully move the filled molds to a secure and level location. Try to keep cylinders out of direct sunlight and in temperatures ranging from 16 to 27 degrees Celsius (60 - 80˚F). Cylinders will weigh roughly 8 lb (4 kg) each. Plan accordingly to transport cylinders to testing facilities. Step 4 Because little information on the strength of concrete mixed in these areas is available, testing results from all groups is appreciated. Break test cylinders after 28 days and send results to Bridges to Prosperity at [email protected]

Volume 3: Suspended

Part 3 - Construction Guide



39

Concrete Quality Control Form Bridge Name: Country: Concrete Competent Person: Source of water?

Is it transparent?

Was the sand produced on-site or delivered?

If produced on-site, is it clean and free of debris?



If produced on-site, is it clean and free of silt and clay?

Was the gravel produced on-site or delivered?

If produced on-site, is it clean and free of debris?

Briefly describe mixing method used:

NOTES:

Volume 3: Suspended

Part 3 - Construction Guide



40

Concrete Quality Control Form

Date

Mix Proportion

Location on Bridge

Accelerator used? If yes, how much?

Measured Slump

Were cylinders taken?

Competent Person Approval

*Approval by the “competent person” requires witness of proper proportioning, mixing, and placement of concrete.

Volume 3: Suspended

Part 3 - Construction Guide



41

Stone/Rubble Masonry Tools Required • Chisel • Hammer • Square • Trowel • Plumb bob • Level • String There are some important factors that contribute to a masonry structure being strong and long lasting. Use as many stones as possible and as little mortar.

• Always fit the stones in place first before mixing mortar to ensure freshness. • Additional dressing may be required to ensure proper fit. • Try not to use shims or small rocks to balance a stone in place; prepare the stone so that it fits without assistance.

• Pack the mortar around the stones with the masonry trowel or fingers to ensure there are no gaps. • Always stagger each layer of masonry as is shown to the right. • Try to place large stones so that their large face is facing down.

Good masonry uses 5cm or less of mortar between joints. Staggering the layers (alternating joints) so that joints are not above each other is also key to strong masonry structures. Un-reinforced, stone masonry walls should not exceed 2 meters in height. If walls larger than this are required, build the first 1 meter 70cm thick, the second 1 meter 50cm thick and the last 1 meter 30cm thick with the grading on the outside of the wall.

Volume 3: Suspended

Part 3 - Construction Guide



42

C.M.U Masonry Tools Required • Trowel • Plumb bob • Wood formwork • Nails • Level • String • Square • Hammer There are some important factors that contribute to a masonry structure being strong and long lasting. • Make sure blocks are wet before applying (in order for mortar to bond) • Mix as little mortar as possible at a time to ensure freshness • Mortar between blocks should not be thicker than 1-2cm • Pack the mortar around the blocks with the masonry trowel or fingers to ensure there are no gaps • If hollow blocks are being used, each block must be filled with concrete • Always stagger each layer of masonry as shown below In some instances, masonry walls will need to be reinforced for additional stability. In the case of most suspended bridges, this is not needed. If additional reinforcement is deemed necessary i.e. working outside the B2P standard drawings, a qualified engineer should be consulted. B2P does NOT recommend using CMU masonry for approach ramp walls to avoid blow-out failure. Also, be aware of the quality of the CMUs that are available locally. The quality and therefore strength of these can vary greatly from site to site. In most cases these blocks are used as formwork, so long as they can withstand the lateral pressures from the wet concrete. Note the size of locally available block and plan wall dimensions accordingly. It is ideal to use whole blocks instead of having to break or cut blocks to fit dimensions.

Volume 3: Suspended

Part 3 - Construction Guide



43

Main Cable Inspection and Care If using re-purposed wire rope, all cables must be inspected before they are considered adequate for use on a B2P bridge project. Cable Inspection It is imperative that the cable that is to be used is thoroughly checked. This can be more of an issue when using donated cable. Know that if the cable is from B2P, it is re-purposed. Important items to check the cable for: • Welded joints • Kinks • Individual wire breaks Individual Wire Breaks A careful inspection of the rope should be done to identify any broken wires. Unwrapping Cable Take care when unwinding the cable from the spool. Kinks in the cable are detrimental to the material strength and are a point of weakness. Furthermore, take care not to lay the cable in sandy areas. Sand may get in between the cable strands and cause damage. Use heavy tie wire to wrap around the loose ends of the cable to stop unraveling if any cuts in the cable are made (note that the wire should be placed on both sides of the cut).

*Consult the Wire rope users manual for more information on how to take care of and inspect wire rope.

Volume 3: Suspended

Part 3 - Construction Guide



44

Clamping and Cable Crush Clamp Material Properties There are two types of clamps that are readily available for cable terminations; forged clamps and malleable clamps. Note the these clamps can be referred to as clips, U-bolts, bulldog clamps, etc. Forged clamps are made from a solid piece of steel that is heated until the metal is soft and then bent to shape. With malleable clamps, the metal is heated until it is liquid and then poured into a form. In this process, there are chances of voids being created or imperfections existing in the clamps that cannot be easily detected. For this reason, malleable clamps are not permitted on B2P projects for use on the main cables. Note that Crosby clamps are forged clamps and are used on all B2P projects. Also note that “drop-forged” is a type of forging process.

DROP-FORGED CLAMPS ARE OF SUPERIOR QUALITY AND MUST BE USED ON ALL B2P PROJECTS.

Red is Dead Never Saddle a Dead Horse

Malleable clamps are inferior to forged clamps and are not suggested for any bridge use. If no drop-forged clamps are available, no clamp size greater than 1 1/8” is recommended. Note that the required torque for malleable clamps is far less than drop-forged and over tightening malleable clamps will lead to clamp failure. The use of malleable clamps requires re-tightening and additional clamps. As such, if using malleable clamps, leave at least half of the clamps permanently above ground.

Volume 3: Suspended

Part 3 - Construction Guide



45

Clamp Torque and Spacing Ensuring that the cable clamps are properly tightened is the single most important quality control issue for bridge construction. If the clamps are not tightened sufficiently, they will not make a proper connection and could cause failure as a result. The required torque varies depending on the quality of the clamp, so be sure to always refer to the manufacturer’s specifications. The table to the right is from the Crosby Group and is intended to be used in conjunction with Crosby clamps. It is always recommended that manufacturer’s guidelines be followed for the clamps that will be used on any given project. If a torque wrench is available, read the amount of torque applied by tightening the nuts similar to a typical wrench. Do this by reading the side gauge and continuing to tighten until specified torque is reached. If a torque wrench is not available, tighten until the diameter of the dead cable is reduced approximately 25%. This reduction in area is what makes this type of connection work.

Cable Diamter (mm) 3.2 4.8 6.4 7.9 9.5 11.1 12.7 14.3 15.9 19.1 22.2 25.4 28.6 31.8 34.9 38.1 41.3 44.5 50.8 57.2 63.5 69.9 76.2 88.9

Cable Diameter (inch) 1/8 1/5 1/4 1/3 3/8 4/9 1/2 4/7 5/8 3/4 7/8 1 1 1/8 1 1/4 1 3/8 1 1/2 1 5/8 1 3/4 2 2 1/4 2 1/2 2 3/4 3 3 1/2

Spacing (mm) 19.2 28.8 38.4 47.4 57 66.6 76.2 85.8 95.4 114.6 133.2 152.4 171.6 190.8 209.4 228.6 247.8 267 304.8 343.2 381 419.4 457.2 533.4

Drop-Forged Clamps Quaninty Required Torque (foot-lbs) 2 4.5 2 7.5 2 15 2 30 2 45 2 65 3 65 3 95 3 95 4 130 4 225 5 225 6 225 7 360 7 360 8 360 8 430 8 590 8 750 8 750 9 750 10 750 10 1200 12 1200

Since the torque required for the clamps will reduce the cross-sectional area of the wire rope, it is important that the clamps are properly oriented. Clamps must be placed such that the saddle is around the live or loadbearing cable and the pinched side is the loose or ‘dead’ cable as shown in the diagram below. The common expression for remembering this is, “Never saddle a dead horse.”

The above figure demonstrates clamps with the proper orientation

Volume 3: Suspended

Part 3 - Construction Guide



46

SECTION 4: MATERIAL PREPARATION 4.1 REQUIRED MATERIALS

On most suspended projects, the materials needed for construction will be divided into two groups: materials that are readily available on or near site, and materials that will require transportation to site. Local Construction Materials All local construction materials should be prepared on site before starting construction. A construction sequence and project management plan should be created and shared with all project stakeholders. Contingency for materials acquisition should be accounted for in the schedule, in particular with critical path elements. Consult the material quantity estimate in Volume 3.1: Suspended Design, Section 3: Material Estimate to ensure quantities are correct. Delivered Construction Materials All construction materials that cannot be found on site should be purchased and delivered to site before starting or during construction. These materials also need to be included in the construction sequence and project management plan. Contingency for materials acquisition should be accounted for in the schedule, in particular with critical path elements. Consult the material quantity estimate in Volume 3.1: Suspended Design, Section 3: Material Quantities to ensure quantities are correct.

Volume 3: Suspended

Part 3 - Construction Guide



47

Local Materials

Tools Required • Hammers

• Buckets

• Grain sacks • Chisels

Local Materials Broken Stone The broken stone is used for the fill in the approach tiers. Broken stone needs merely to be available on the site. It is recommended that broken stone is collected prior to needing it for fill. No further preparation to the stone is required. Dressed Stone In some areas, dressed stones are widely used in construction. If this is the case, dressed stones can be used in place of CMU masonry block. The decision to use these should be based solely on the area where the bridge will be and the local construction techniques. Dressed stone is dressed to be square with hammers and chisels. There are two types of dressed stones: Corner Stones: Two adjacent sides of a stone need to be cleanly chiseled and square for use at the corners of the towers. Stones should be approximately 20cm x 28cm. Face Stones: The face of one side (of a generally four sided stone) needs to be cleanly chiseled straight and square as it will be placed facing out from the masonry work. Stones should be approximately 20cm x 28cm. Consult the drawings in Volume 3.2 Suspended Drawings to determine how many of each dressed stone type will be needed to match the number of CMU blocks required, as specified in the drawings. If these replace the CMU block that are used as formwork, the inside dimensions of the walls must be kept the same as well as the height to ensure the same amount of concrete is poured.

Volume 3: Suspended

Part 3 - Construction Guide



48

Gravel

Sand

The coarse aggregate (gravel) will be used in the concrete and should be rough and clean with broken faces; rounded particles will not adhere well in the mixture and should be avoided if possible. Dirt and organics in the mixture will also decrease mix strength, and any aggregate containing soils must be washed until clean. Riverside gravel should be broken with a hammer to form rougher surfaces. Maximum recommended gravel size is 5cm, but is usually smaller and dependent on the formwork and dimensions of the rebar. Aggregates larger than 5cm will usually reduce concrete strength. Gravel can be collected from river deposits or by breaking boulders into the necessary size.

The sand will be used for the concrete mixture, mortar and the sand sizes should be well graded. The best design has 50% medium size particles (~2mm) with decreasing amounts of very large and very small particles. Thus, if there is a supply of very fine sand (such as found in many beaches), it should be thoroughly mixed with coarser sand from another location. Sand can be collected from river deposits or from a quarry. The quality of the sand should be assessed before collection. Check the sand for impurities such as mud, clay, debris, silt, and avoid sand with a high content of these materials to reduce the need for washing. Sand with silt must be washed out in grain sacks in the river before use. Note: Silt is a material that when rubbed between your fingers leaves a colored smear, yet lacks the earthen smell of organic soils. Silt must be avoided in sand mixtures.

Water

The water used for concrete is often times not potable water. This being said, it is important that the water is relatively clean. Many times, the only water available in the quantities needed is river water. In this case, make sure that the water has a low turbidity and is mostly transparent. If the water has a higher turbidity (cloudy), it should not be used directly. One way to deal with turbid water is to have a holding container for the river water on both sides. While the water is in the container, some of the impurities will settle to the bottom, making the water on top clearer. There are many other ways to deal with high turbidity so do what makes sense for a given site.

Volume 3: Suspended

Part 3 - Construction Guide



49

Delivered Materials

Cement

It is important to buy cement from a trusted store in the area. It is more likely that the cement is stored properly and is not stored for very long. If cement is not properly stored, there can be sizable decreases in the strength. Even when properly stored, the cement can lose up to 50% of its strength in 18 months of storage! Check for hard spots in the cement bag. This is an indication that the cement has been exposed to moisture. If hard spots are identified in the bags of cement, the bag should not be used. Exposure to water can also greatly effect the strength of the cement.

Gravel

Sand

Cable

If gravel is purchased, the same specifications as previously stated apply (5cm maximum size).

When silt-free sand cannot be found on site, sand will have to be purchased. This is necessary only if there is no locally available sand or if the locally available sand does not meet the specifications as previously stated.

The cable (wire rope) must be sourced in-county from either B2P, a local supplier or a local importation company. Once in country, the cable must be delivered to site. Develop a rough estimate of how much the cable will weigh before arranging transportation, as the size of the truck size will be dependant on the total weight and volume.

Cable Clamps

ONLY drop-forged clamps are permitted for use on B2P projects. Drop-forged clamps are usually not available locally and should be brought from the United States or Europe.

Volume 3: Suspended

Part 3 - Construction Guide



50

Timber

Timber will be needed for the decking, crossbeams and the nailers (if used). B2P standard decking boards for these bridges are not standard lumber sizes so they may have to be cut specifically for the project. Since the quality of timber can vary, and delays in getting the timber are not uncommon, it is best to plan ahead.

Steel Crossbeams (if used)

If steel crossbeams are used, they need to be sized or checked by an engineer, preferably a B2P Bridge Corps or Technical Advisory Board member.

Reinforcement Steel

Reinforcement steel is specified for the anchors and towers, pedestals and suspenders. Rebar is usually available almost anywhere, but rebar from larger cities tends to be of better quality. Also take note of maximum lengths of rebar available.

CMU Blocks

CMU Blocks are typically used for the pedestals and approach ramps. Take note of the available dimensions as they may differ from those specified in the drawings.

Volume 3: Suspended

Part 3 - Construction Guide



51

Materials List:

X

Material Item

Quantity Required

Date of delivery to site

Notes

Local Materials Sand Stones Gravel (crushed stone) Construction Materials Cement bags for Tower Cement bags for Anchor Cement bags for Approach Cement bags for Tiers Masonry blocks for Towers Steel reinforcement bar 10 mm Ø (6m pieces) Steel reinforcement bar 13 mm Ø (6m pieces) Steel reinforcement bar 16 mm Ø (6m pieces) Steel reinforcement bar 19 mm Ø (6m pieces) Handrail Cable, diameter __________ Walkway cable, diameter __________ Clamps, drop-forged

Volume 3: Suspended

Part 3 - Construction Guide



52

Recommended Tool List:

Item/Tool

Quantity Recommended

Shovel Pick

4 2

Excavation bar Wheelbarrow 20 liter (5 gallon) buckets Machete Measuring tape, 5 meters Masonry tools (if not provided by mason) Woodsaw and blades Hacksaw and extra blades

2 2 12 1 2 2 sets 1 2

x

Item Hammers 100 meter tape Bendable plastic tubing Suspender rebar Rebar Calculator with Sine & Cosine Rock chisel Roofing tar Flagging stakes Vice grips

Quantity 5 1 see drawings see drawings see drawings 1 4 5 Gallons 20 2 4 min. 1 per crossbeam 1

2 kg sledgehammer 4 kg sledgehammer (if stone work)

1 1

Rice sacks 4” screws or lag bolts

Wrench; minimum 3 foot, socket size same as cable or socket wrench with breaker bar Hand drill and bits; reference decking drawings to locate sizes. Masonry string 10 meter rope Spray paint Pipe to bend suspenders Plastic tarp Tamper for backfill Pliers

2

Abney Level or Auto Level

1

Diamond shape trowel

4

1 1 1 1 1 1 1

Formwork / Visuals Plumb bob

1

Volume 3: Suspended

Part 3 - Construction Guide

x



53

SECTION 5: SITE PREPARATION 5.1

EXCAVATION LAYOUT

Tools Required • Spray paint

• Shovels • Automatic level and tripod (if available) • String and picks • Stakes • Plumb bob • Machete • Hammer • Nails

Step 1

Using the markers R and L on the right and left side of the river respectively, as marked in the survey, measure the distance from R (or L ) to the front of the tower, according to your design. If an automatic level is available, use it to establish the bridge centerline from side to side, then set all subsequent points off of the established center line. Place a stake at the point of Front of Foundation, named FOF(R) - Front of Foundation Right.

Step 2

Find the distance between the front of the foundation to the back of the anchor in your plans and place another stake at that point. Finally, go back 2.00m further and place another stake (a). This stake is the permanent centerline marker and thus needs to be placed firmly so as not to move during construction.

Volume 3: Suspended

Part 3 - Construction Guide



54

Step 3

Repeat the process on the other side of the river. Verify both sides are square to each other. Run a string between the permanent centerline stakes.

Step 4

Measure the distance from front of foundation (FOF) to front of anchor (FOA) and mark FOA(R).

Step 5: the 3-4-5 method

The four corners of the foundation and anchor blocks respectively are found from the centerline. Using a 12 meter string, connect at FOF(R), and have one person hold the 4.0 meter mark of the string along the centerline. The second person holds the string at 9.0 meters, repositioning until the remaining 3.0 meters can reach back to the start point, creating a 3-4-5 triangle. The relative dimensions of the triangle create a right angle along the 3m leg. Stake this point, “1.” Repeat for all corner points for both foundation and anchor.

Step 6 Extend string around these four stakes at each of the towers and anchors. These are your excavation areas.

Volume 3: Suspended

Part 3 - Construction Guide



55

5.2 EXCAVATION IN SOIL Step 1

Excavate the area indicated in the foundation layout level.

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Step 2

Dig the anchor trench according to the measurements given in the plans. If applicable, ensure that proper sloping is used. PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Step 3

Dig out the access trenches to the anchor. *Note, anchors are often excavated after the towers have been completed. PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Part 3 - Construction Guide

PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

Volume 3: Suspended



56

5.3

EXCAVATION IN ROCK

The method of marking “front of foundation” (FOF(R)) and front of anchor (FOA(R)) is the same as described in section 5.2 - Excavation in Soil.

Foundations placed on solid rock bed do not require excavation to one meter (1m) depth. This can likely be reduced to ~30cm but engineering judgement should be used. Ensure the rock surface beneath towers and foundation areas is rough, but clean of debris and organic materials such as soil and brush, so it will bond to the first layer of cement. Soft rock anchors require excavation to one meter (1m) depth, but do not need to be at the same level as the tower excavation. Excavate a soft rock anchor according to the dimensions in your design. Since stakes can be hard to use, use spray paint to mark the excavation area.

Volume 3: Suspended

Part 3 - Construction Guide



57

QUALITY CONTROL CHECKLIST: SITE PREPARATION Initial to confirm that each step has been completed Step Reference/Guide Layout Step 1 Steps 2-3 Step 4 Step 2 Step 5

Mason/ Construction Manager

-------------------------------------------------------------------------------------------------------------------------------------------Survey points marked with permanent spray paint or other defined marker?

After Step 3

Centerline established using automatic level (if available) and marked with stringline? Bridge span confirmed using laser distance finder (if available)? Permanent control stakes placed along centerline? Excavation layout indicated with stakes and string, or spray paint for rock? -------------------------------------------------------------------------------------------------------------------------------------------Excavation depth consistent with plans?

After Step 3

Excavation width consistent with plans?

After Step 3

No water allowed to enter excavation?

After Step 3

If water is in excavation, have drainage systems been constructed?

Excavation

As-Builts

-------------------------------------------------------------------------------------------------------------------------------------------Measurements taken for as-builts

Tech. Supervisor

------------------

------------------

------------------

------------------

------------------

------------------

------------------

------------------

QC photos taken

Safety

-------------------------------------------------------------------------------------------------------------------------------------------Proper benching

Name of Mason/Construction Manager : Name of Tech. Supervisor: Volume 3: Suspended

Part 3 - Construction Guide



58

SECTION 6: CONSTRUCTION 6.1 BRIDGE TERMINOLOGY GUIDE

Volume 3: Suspended

Part 3 - Construction Guide



59

6.2 FOUNDATION & TIER CONSTRUCTION Tools Required • String • Shovels • Square



• Plumb bob • Buckets



Materials Required • Cement • Gravel (crushed stone) • Sand

• Water level • Masonry tools

• Hammer dressed stone or CMUs • Broken stone (rock fill)

Step 1 Ensure that the foundation excavation is level from front to back, side to side. Ensure that the foundations on either side of the river are square to one another. Always use the centerline for positioning.

Step 2 Pour a foundation layer, 20cm (8’’), of concrete onto the soil at the base of the foundation. In the case of hard rock, pour a thick mortar mixture to roughened rock area.

Volume 3: Suspended

Part 3 - Construction Guide



60

Step 3 Place the first four (4) corner-stones of the foundation tier (dimensions of foundation tier according to plans). Ensure the stones are placed square using a plumb bob and level using a water level.

Step 4 Fill the layer of masonry stones between the corner stones around the perimeter of the foundation tier, placing stones as closely together as possible. The wall should be 30cm thick. To ensure that the walls remain straight and keep a consistent thickness, string should be tied between the corner stones to act as a guide.

Step 5 Continue with the masonry layers until the tier has reached 1.00m in height.

Volume 3: Suspended

Part 3 - Construction Guide



61

Step 6 Fill the foundation within the masonry walls with available rock. Put a layer of bigger stone and fill the gaps with smaller stone, then add another layer of bigger stones and so on. This fill should be done in 3 equal layers (~30cm).

Step 7 Using a tamping rod, fill the voids between stones with sand and gravel. This should be done after each layer.

Step 8 Make a watery grout of cement/sand mix in 1:2 proportion out of 2 cement bags and pour over the foundation to help the stone fill stick together. This should also be done after each layer. Finally, pour a thin concrete slab of approximately 0.70 meters wide around the edges as a base for the next course of stone masonry to sit on. * Wire mesh can be added for reinforcement, as it distributes the load of the above tier or tower

Volume 3: Suspended

Part 3 - Construction Guide



62

Step 9

AS YOU BUILD UP THE TIERS, RECONFIRM THAT EACH TIER IS TRUE TO THE CENTERLINE BEFORE CONSTRUCTION OF THE SUBSEQUENT TIER BY MARKING THE CENTERLINE ON THE FOUNDATION OR TIER BELOW. Continue with each tier as specified by the construction drawings. Each tier reduces in width and length from the one below it (per stand drawings), but a wall thickness of 30cm remains constant.

Volume 3: Suspended

Part 3 - Construction Guide



63

QUALITY CONTROL CHECKLIST: FOUNDATION & TIER CONSTRUCTION Initial to confirm that each step has been completed. Step Reference/Guide

Mason/ Construction Manager

Step 1

-------------------------------------------------------------------------------------------------------------------------------------------Foundation corners square to centerline?

Step 2

Foundation filled with rock (not soil) and grout?

Foundation

Steps 3-5

Tech. Supervisor

------------------

------------------

------------------

------------------

------------------

------------------

------------------

------------------

Foundation minimum depth 1.0 meter? No water allowed to enter excavation upon completion?

Tier/s Step 3 Before Step 4 Ongoing

As-Built

-------------------------------------------------------------------------------------------------------------------------------------------Each tier corner is set square to the centerline? Actual dimensions taken for as-builts? All concrete used within 60 minutes of mixing? (Foundation and Base slabs) -------------------------------------------------------------------------------------------------------------------------------------------As-built measurements were taken for this section QC photos taken

Safety

-------------------------------------------------------------------------------------------------------------------------------------------All near-misses and incidents were documented

Name of Mason/Construction Manager : Name of Tech. Supervisor:

Volume 3: Suspended

Part 3 - Construction Guide



64

6.3 TOWER CONSTRUCTION



Tools Required • String • Plumb bob • Shovels • Buckets • Square • Wire cutters

• Steel hacksaw • Masonry tools • Level

Materials Required • Cement • Sand • Gravel • Hammer dressed stone or CMU • Tubing • Tie Wire • 2 x ~14” tire rims to be cut in half for handrail saddles. • 4 pieces of rebar, 19mm (#6) Ø x 4.50m length • 67cm long, 7.5cm (3”) angle iron • Rebar guides for walkway cables: (optional) # of walkway cables + 1, 16 mm Ø x 20cm each



Volume 3: Suspended

Part 3 - Construction Guide



65

Step 1 Align Towers The alignment of the towers, perpendicular to the bridge centerline, is extremely important, as the cable running over the saddles must not impose a side or lateral force on the towers. Even if the tiers are skewed, it is crucial that the towers be parallel to one another and perpendicular to the centerline. For that, all measurements should be based on the centerline. The base of the two symmetrical towers is dimensioned 1.00 meter long x 2.80 meters wide.

Step 2 Set Corners Place the four outside corner-blocks ensuring they are level and square relative to the centerline. Create a second tower centerline to work from, and verify dimensions from centerline are level and square.

Volume 3: Suspended

Part 3 - Construction Guide



66

Step 3 Build Tower Base Build the first level of masonry, 20cm in height, around the entire perimeter of a tower (2.80m x 1.00m). When using CMUs, 20cm is the height of a typical block.

Step 4 Insert Steel Rebar For each side, 2 pieces of 19mm Ø rebar should be bent in a U shape per diagram below. Place the two rebar into the cavity formed during Step 3 and cover with concrete. Bars should be placed 12cm c/c (~14cm from the inside face of the CMU wall).

Volume 3: Suspended

Part 3 - Construction Guide



67

Step 5 Complete Tower Construction and Fill Towers should be built to 1.00m x 0.70m to 1.00m tall above first masonry layer (1.2m above tier) on each side. Build the masonry for the tower 20-40cm in height and fill with concrete, repeat the process until reaching the needed height. Fill to 10cm below the top of the towers. The rebar should be slightly extending from tower. Use specified concrete mixture ratio 1:2:3. Verify with the concrete mixing guideline in Volume 3.3 Section 2 - Quality Control.

Step 6 Complete the Walkway Hump and Install Angle Iron (For use of fabricated saddles, go to step 7) Between the towers, complete concrete fill to 20cm hump above the masonry perimeter (40cm from floor of tower). Insert the 67cm long x 7.5cm (3”) angle iron at the top of the hump. Make sure the placement is perpendicular to the bridge centerline and flush with the top of the hump curve. This steel surface will act as a frictionless surface for the walkway cables, as the elastic cable is expected to stretch under loading conditions.

Volume 3: Suspended

Part 3 - Construction Guide



68

Step 7 Complete the Walkway Hump and Install Fabricated Walkway Saddle (optional) Between the towers, complete concrete fill to 20cm hump above the masonry perimeter (40cm from floor of tower). Measure and mark 58 cm from either side of center point (center between the 2 towers) and place the fabricated saddle. This is the inner-most dimension for the saddle. From the centerline the guides should be placed at 58cm, 63cm, and 68cm respectively. This steel surface of the saddle will act as a frictionless surface for the walkway cables, as the elastic cable is expected to stretch under loading conditions.

Step 8 Form Tire Rim (Handrail saddle)

The handrail saddles must sit 1.10 meters above the walkway saddles (1.40m above tower floor), so form accordingly. Cut a used tire rim in half. Install the tire rims (or prefabricated handrail saddles) so that the cable will cross at 25cm from the inside of the tower and 40cm from the front of the tower on the anchor side. Build up to the hump with concrete 1:2:3. Make sure handrail saddles are level side to side. Make sure the inside on the rim is completely filled with concrete. Finish with smooth masonry mortar. Be sure not to leave gaps on the side or beneath the rim as shown correctly finished in the lower right photo.

Volume 3: Suspended

Part 3 - Construction Guide



69

QUALITY CONTROL CHECKLIST: TOWER CONSTRUCTION Initial to confirm that each step has been completed Step Reference/Guide

Mason/ Construction Manager

Step 1

-------------------------------------------------------------------------------------------------------------------------------------------Centerline alignment used to lay out both towers?

Step 1

Actual height difference (ΔH) and span between top of tiers confirmed as built?

Pre-Construction

Steps 2-5

-------------------------------------------------------------------------------------------------------------------------------------------Height difference on L side between walkway and handrail saddles equal to 1.10 meters

Steps 2-5

Height difference on R side between walkway and handrail saddles equal to 1.10 meters

Step 6/7

Angle iron or fabricated walkway saddles (if used) aligned with centerline and level?

Construction

Step 8 Before Steps 4-5

Tech. Supervisor

------------------

------------------

------------------

------------------

------------------

------------------

------------------

------------------

Handrail saddles aligned with centerline and level? Rebar used: sizes, lengths and numbers - verified with drawing set? Concrete QC form completed?

As-Built

-------------------------------------------------------------------------------------------------------------------------------------------As-built measurements were taken for this section QC photos taken

Safety

-------------------------------------------------------------------------------------------------------------------------------------------All near misses and incidents were documented

Name of Mason/Construction Manager : Name of Tech. Supervisor: Volume 3: Suspended

Part 3 - Construction Guide



70

6.4 ANCHOR CONSTRUCTION & CABLE INSTALLATION There are two anchor types discussed herein: gravity and drum. The latter is only used for soft-rock conditions with spans less than 60 meters. All other bridge scenarios require a beam type anchor. Gravity Anchor All Soil and Soft Rock Conditions for spans up to 120 meters ‘Small’ Anchor = Spans up to 60 meters ‘Large’ Anchor = Spans from 61 to 120 meters Tools Required • String • Shovels



• Plumb bob • Buckets

• Water level • Wire cutters

• Wrench or breaker bar with cheater bar (1 meter +) • Socket to fit forged clamps



Materials Required • Cement • Sand • Gravel • Tie wire • Plastic tubing • Cable (cable size per specifications from cable look-out tool) • Drop forged cable clamps (for cable clamps size and quality see design guide) • Steel rebar: per design drawings

*Designating Anchor with Erection Hook • If a bridge has one rock drum anchor and one gravity anchor on the other side, the gravity anchor is the adjustable anchor. As such, ensure the erection hook is attached to the beam anchor. • If a bridge has two of the same type of anchor (gravity or drum), the lower elevation anchor is the adjustable anchor. As such, ensure the erection hook is attached to the lower elevation anchor.

Volume 3: Suspended

Part 3 - Construction Guide



71

Step 1 Build Beams Tie together the straight steel rebar with square ties per the following quantities and dimensions: Small beams: Spans less than 60 meters • 4 straight bars, 19mm Ø, 2.90m in length • 11 square rings, 10mm Ø, cut to 2.20m each, bend into squares 0.50 m per side • 3 pre-bent erection hooks, 16mm Ø, 2.5m in length* (varies depending on rebar bending capabilities)

Large beams: Spans greater than 61 meters to 120m • 8 straight bars, 19mm Ø, 2.90m in length • 11 square rings, 10mm Ø, cut to 3.4m each, bend into squares 0.80m per side • 3 pre-bent erection hooks, 16mm Ø, 3.0m in length* (varies depending on rebar bending capabilities)

Step 2 Add Erection Hooks Tie 3 erection hooks ONLY to the anchor that will be adjustable. Again, if two similar anchor types are used (drum or beam), the lower elevation is adjustable. If one drum and one beam anchor is used, the beam is the adjustable side. Attach the bent rebar erection hooks 0.80 meters from either end of the rebar cages. A cable winch will attach to the hooks while setting cable sag, so ensure the hooks are well secured. * As 3 deck cables are used it’s advisable to add the third erection hook in the middle of the rebar cage.

Volume 3: Suspended

Part 3 - Construction Guide



72

Step 3 Lay out Cable and Add Tubing 1. Lay out the cable to either side of the river. Drop the cables into the excavation pit, in line with crossing points at tower. 2. Feed the walkway cables through 1.00m pieces of tubing (flexible hose) placed at each tower. 3. At the adjustable side, feed the cables through 4.00m long x 6-7cm diameter tubing (flexible hose) and place tubing in pit. The non-adjustable side does not require tubbing.

Step 4 Place Anchor Beams Set the anchor beams in the excavation on top of the cables. The anchor cage should sit at an angle approximately equal to the backstay angle so the front face with the erection hooks is perpendicular to where the cable will come off the towers. It is helpful to prop the beam with rocks to allow the anchor to sit at the angle.

Step 5 Pull Cable Over Anchor Each cable needs to wrap around the anchor and extend back towards the tower with the loose end sitting in the approach area. Care needs to be taken to ensure the location of each cable is aligned with its respective saddle and where it will stay when the bridge is done. A pre-measured alignment board may be helpful. Once secured, the cable must come off either the walkway or handrail saddle and follow a straight path to the anchor.

Volume 3: Suspended

Part 3 - Construction Guide



73

THIS IS THE MOST CRITICAL STEP OF CONSTRUCTION. DO NOT PROCEED WITHOUT PROPER DROP-FORGED CLAMPS, SOCKETS AND WRENCH WITH CHEATER BAR. Step 6 Cable Clamps With the dead end of the cable (cut end) sitting on top of the live end (extending to tower and across bridge), install the cable clamps per the specified numbers and spacing, and hand-tighten. For information on the number of clamps to use and the spacing between clamps see Volume 3.3 Section 6.6: Cable Clamps Installation. Ensure that the clamp saddle lies against the live-end of the cable. Immediately fully torque the nonadjustable anchor side (the side without erection hooks) using a wrench or breaker bar with a minimum 1 meter extension (cheater bar) until the dead end of the cable has a reduced cross-sectional area of at least 25%, as shown bottom left. On the adjustable side put minimum of 2 clamps per cable and hand-tighten. Note: Cables should not be under tension when pouring the anchors.

Red is Dead Never Saddle a Dead Horse

Volume 3: Suspended

Part 3 - Construction Guide



74

Step 7 Pour Anchor Pour the fixed side (no tubing, no erection hooks) first. Fill the anchor excavation pit to 1.0 meter depth with concrete, ensuring the entire anchor cage is submerged in at least 10cm of concrete. Use the specified concrete mixture ratio 1:2:3, verify with the concrete mixing guideline in Volume 3.3 Section 2 - Quality Control. Take care to tamper the concrete mixture to ensure no pockets of air remain. Repeat for the adjustable side, ensuring no concrete gets into the tubes and that the tube ends remain exposed. NOTE: If the excavation is too big, use formwork on the rear side of the anchor.

Do not backfill the nonadjustable side until sag is set. Cables must be completely free when setting sag.

Volume 3: Suspended

Part 3 - Construction Guide

Do not backfill the adjustable side until the deck is on and the bridge is complete, in case adjustments need to be made.



75

Drum Anchor (Rock conditions) Tools Required • String • Shovels

• Plumb bob • Buckets

• Water level • Wire cutters



Materials Required • Cement • Sand • Gravel • Tie wire • Plastic tubing • Cable (cable size per specifications in the cable look-up tool) • Drop forged cable clamps (for cable clamps size and quantity see table in volume 3.2 or manufacture specification) • Steel rebar: - Spans 40 meters or less - Anchor rods, 16 pieces, 25mm Ø , cut at 1.50 meters - Inner drum: 8 pieces, 10mm Ø, cut at 3.40 meters, bent into circle 0.90 meter Ø - Outer drum: 8 pieces, 10mm Ø, cut at 5.25 meters, bent into circle 1.50 meter Ø - Erection hook: 1 piece, 16mm Ø, cut at 2.0 meters, bent into hook - Spans greater than 40 meters and up to 60 meters - Anchor rods, 20 pieces, 25mm Ø, cut at 1.50 meters - Inner drum: 8 pieces, 10mm Ø, cut at 4.15 meters, bent into circle 1.15 meter Ø - Outer drum: 8 pieces, 10mm Ø, cut at 5.90 meters, bent into circle 1.70 meter Ø - Erection hook: 1 piece, 16mm Ø, cut at 2.5 meters, bent into hook

NOTE: When using a drum anchor on spans 40 meters or less, the cable is continuous. The first end of the cable starts at the adjustable side. Once taken across the river, it is wrapped around the fixed drum anchor one full rotation and a half (540 degrees) and is returned back to the adjustable anchor side. When using a drum anchor on spans greater than 40 meters, but less than the maximum 60 meters, the cable is cut into two pieces. As such the cable sag setting procedure is different for the two types.



Volume 3: Suspended

Part 3 - Construction Guide



76

Step 1 Excavation Excavate a cylindrical pit to a depth and distance from the tower as specified in the drawings. It is critical to leave the edge closest to the towers as clean and sharp as possible. The depth of excavation is also critical to the design.

Step 2 Build Cages Place the vertical anchor rods as shown in to the diagram below. First tie together the outer rebar cage with 10mm rebar specified for the outer drum. (Note: ‘Small’ drum sizes for spans less than 40 meters, ‘large’ drum sizes for spans greater than 40 meters.)

Required Diameters Outer Drum

Medium 41-60 m

Small 0-40 m

Dia. Drum

Inner Drum

Dia. Rod Dia. Drum

Dia. Rod

Total Volume (m3)

Total # Rods (25mm)

160

145

100

85

6.25

16

180

165

125

110

5.18

20

Small Drums: Span 0 - 40 meters • Anchor rods, 16 pieces, 25mm Ø, cut at 1.50 meters • Inner drum: 8 pieces, 10mm Ø, cut at 3.40 meters, bent into circle 0.85 meter Ø • Outer drum: 8 pieces, 10mm Ø, cut at 5.25 meters, bent into circle 1.45 meter Ø Medium Drums: Span 41 - 60 meters • Anchor rods, 20 pieces, 25mm Ø, cut at 1.50 meters • Inner drum: 13 pieces, 10mm Ø, cut at 4.15 meters, bent into circle 1.10 meter Ø • Outer drum: 7 pieces, 10mm Ø, cut at 5.90 meters, bent into circle 1.65 meter Ø

**If large anchors are need, seek additional design guidance from an engineer.

Volume 3: Suspended

Part 3 - Construction Guide



77

Step 3 Add Erection Hooks Tie two erection hooks to the anchor that will be adjustable. Attach the bent rebar erection hooks 0.50 meters from the top of the outer cage. A cable winch will attach to the hook while setting cable sag so ensure the hooks are well secured.

Step 4 Place Rebar Cages and Pour Inner Drum Place the inner cage inside the excavation pit embedded to the depth specified in drawings, leaving the top of the rebar cage approximately 0.50 meters above ground (on adjustable side, the erection hook must face towards tower). Place the outer cage around the inner cage, attaching vertical rebar to the backside of the drum. Verify both cages are vertical and flush and tie together at the back of the excavation pit, furthest from the tower. The outer cage diameter allows the handrail cables to come off the tower and connect to the anchor at a straight line. The inner drum diameter allows the walkway cables to come off the saddles and connect to the anchor in a straight line. Frame and pour the inner drum with concrete mix proportion 1:2:3.

Step 5 Lay out Cable Lay out the cable to either side of the river. Thread 4.0 meters of plastic tubing on each of the cables on the adjustable side. The non-adjustable side does not need tubing. For spans less than 40 meters, both loose ends must lie on the adjustable end.

Volume 3: Suspended

Part 3 - Construction Guide

For less than 40 meter span (continuous cable)



78

Step 6 Pull Walkway Cable around Anchor Each walkway cable needs to wrap around the inner anchor and each loose end should be placed into the approach area after 180 degree turn. Once secured, the cable must come off the walkway saddle and follow a straight path to the anchor. The cable should wrap around the drum below ground level, at least 75cm from the top of the drum. When using 3 walkway cables the middle one will be wrapped around the anchor drum and tied to itself.

Red is Dead Never Saddle a Dead Horse

Step 7 Clamp Walkway Cables

Tie the walkway cables onto the opposing walkway cable after wrapping behind the anchor. Hand-tighten the cable clamps so the saddle touches the live-end of the cable (Never saddle a dead horse!) Hand tighten the adjustable side. Tighten non-adjustable side to specified torque with minimum 1 meter long pipe or wrench. If clamps are malleable rather than drop forged, clamp failure will occur if taken to an equivalent torque. For spans less than 40 meters, there are no clamps on the fixed end as the cable is continuous. Rather, wrap the cable fully around the respective drum and return to adjustable side.

Volume 3: Suspended

Part 3 - Construction Guide



79

Step 8 Pour the Anchor Fill the excavation pit with concrete aggregate, ensuring the entire rebar cage is covered in at least 10cm of concrete to an elevation of approximately 50cm above the ground surface. Do not fill with rocks. DO NOT USE FORM-WORK BELOW GROUND. Pour on the fixed side first. Take care to tamp the concrete mixture to ensure no voids form. Repeat for the adjustable side, ensuring no concrete gets into the tubes and that the tube ends remain exposed. Let both sides cure a minimum 7 days unless concrete curing accelerator is added.

Step 9 Pull Handrail Cable around Anchor Each handrail must wrap around the outer anchor (both cages should be incased in concrete) and the loose end should be placed into approach area. Once secured, the cable must come off either the walkway or handrail saddle and follow a straight path to the anchor. The cable should wrap around the drum at ground level, ensuring there is 50cm depth from the top of the drum.

Step 10 Clamp Handrail Cables Tie the handrail cable onto the opposing handrail cable after wrapping behind the anchor. Hand-tighten the cable clamps immediately. Torque until the dead end of the cable’s diameter has a reduced at least 25%. If clamps are malleable rather than drop forged, clamp failure will occur if taken to full torque, but cross-sectional reduction is critical. See Suspended Volume 1: Design & Analysis for additional information.

Volume 3: Suspended

Part 3 - Construction Guide

Red is Dead Never Saddle a Dead Horse



80

QUALITY CONTROL CHECKLIST: ANCHOR CONSTRUCTION & CABLE INSTALLATION Initial to confirm that each step has been completed Step Reference/Guide

Mason/Construction Manager

Drum + Beam Construction -------------------------------------------------------------------------------------------------------------------------- ------------------Before Step 1

-----------------Cable clamps drop-forged?

Before Step 1

Width or diameter of excavation verified per construction drawings?

Before Step 1

Depth of excavation verified per construction drawings?

Before Step 1

Quantity and size of anchor rods (rebar) verified per construction drawings?

Before Step 1

No form-work used below ground level on the front side?

Step 6

Cable clamps reduce cable cross-section by 25% for every clamp?

Step 6

Cable spacing consistent and per specifications?

Step 6

Cable clamp saddles on ‘live’ end of cable (the cable in tension from the bridge).

Tech. Supervisor ------------------

Concrete QC forms completed?

Drum Anchor Construction -------------------------------------------------------------------------------------------------------------------------- ------------------Step 6

-----------------Cable wrapped full turn around drum (540 degree)?

Step 4

Diameter of both inner and outer cages flush with saddles when installed on drum?

After Step 1

Front edge of excavation has sharp edge ?

Step 4

0.5 meters of drum formed above ground?

Step 6

Cable wrapped 75cm below top of drum?

As-Built

-------------------------------------------------------------------------------------------------------------------------- -----------------------------------As-built measurements were taken for this section

------------------

------------------

QC photos taken

Safety

Volume 3: Suspended

-------------------------------------------------------------------------------------------------------------------------- -----------------------------------All near misses and incidents were documented

Part 3 - Construction Guide

------------------



81

6.5

CABLE SAG SETTING The Design Sag, B d , is calculated as 5% of span. This value is used in the Distance to Low Point of Cable (f) calculation, which in turn is considered to ensure proper freeboard above the High Water Level. The cable sag is the vertical drop that the cable will dip below a line drawn between each towers, measured as the chord at center span. The cable is hoisted to a lesser sag than is designated due to the elasticity of the cable, as once the cable is set, the self-weight of the bridge will slightly stretch and the bridge will lower towards the river. As such, the final lowest point is calculated using the design sag, B d , but the cable will be set in the field using hoisting sag.

Re-purposed Cable (includes cable donated from B2P program) Percent of Span Design sag ( B d ) 5.00% Hoisting sag ( B h ) 4.60%

f=







(4 ⋅ hsag − ΔH )2 16 ⋅ hsag

f = Distance to Low Point of Cable Bh = Hoist Sag Bd = Design Sag hsag = Bh ⋅ span (m) ΔH = height diff . (m)

Volume 3: Suspended

Part 3 - Construction Guide



82

IMPORTANT SAFETY NOTICES

Cable Winch Safety:

A thorough inspection of the cable winch intended for use in cable sag setting is mandatory prior to use. A failed winch can seriously injure or even kill a person. Never use a winch you do not trust or that has been provided by an unknown source, or one that shows excessive rusting or is broken. Inspection should include: An examination of the chain for wear, twists, excessive dirt, broken links, and proper lubrication. Hooks should be inspected for deformations, cracks, damage, and properly operating latches.

Cable Winch Components • Hook: to attach to the erection hooks • Large chain with hook: to attach to the live cable with either chain or clamp • Hoist chain: to pull through cable winch while hoisting Cable Winch Attachment: • The cable winch should always be attached to the erection hooks. • The cable winch should always be attached so that the cable is being pulled in a straight line between tower saddle and anchor. • The cable winch should never be attached so that when under tension the winch is “floating.” The winch should always be “grounded” during cable sag setting. Additional Safety Concerns: • ONLY active participants in the cable sag setting should be present at site. Spectators only

invite accidents. • Never allow participants or spectators to stand in front of the anchor when cable or cable winch are under tension. • Never use a cable clamp at the saddle to “hold” live cable under tension.

Cable Safety: NEVER leave a cable unsecured! When you are adjusting a cable and therefore releasing its clamps, make sure the tail of that cable is secured to another cable before releasing the clamps. CABLE CAN SLIP - MAKE SURE CLAMPS ARE FULLY TORQUED.

Volume 3: Suspended

Part 3 - Construction Guide

Red is Dead Never Saddle a Dead Horse



83

SAFE ZONES

Safety Zone during cable tensioning

Safe Zones:

Before tensioning cables and putting any load on the winches, determine “danger zones”- areas which are unsafe and should not be occupied during sag setting. Also determine areas which are safe escape routes that should be used in case of emergency and communicate the location of those areas to all workers on the site.

Volume 3: Suspended

Part 3 - Construction Guide



84

Distance to Low Point HOIST ELEVATION, f

Span (m)

Height Differential between abutments (m)

35 0.0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50

40

45

50

55

60

65

70

75

80

85

90

95

100 105 110 115

1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.05 4.09 4.32 4.55 4.77 5.00 5.23 1.63 1.88 2.13 2.38 2.63 2.88 3.13 3.38 3.63 3.88 3.93 3.97 4.19 4.42 4.65 4.88 5.10 1.51 1.76 2.10 2.26 2.51 2.76 3.00 3.25 3.50 3.75 3.80 3.84 4.07 4.30 4.53 4.75 4.98 1.40 1.64 1.89 2.14 2.39 2.64 2.89 3.14 3.38 3.63 3.68 3.72 3.95 4.18 4.41 4.63 4.86 1.29 1.53 1.78 2.03 2.27 2.52 2.77 3.02 3.27 3.52 3.57 3.61 3.83 4.06 4.29 4.51 4.74 1.18 1.42 1.67 1.91 2.16 2.41 2.66 2.90 3.15 3.40 3.45 3.49 3.72 3.94 4.17 4.39 4.62 1.08 1.32 1.56 1.81 2.05 2.30 2.54 2.79 3.04 3.29 3.34 3.38 3.60 3.83 4.05 4.28 4.50 0.98 1.22 1.46 1.70 1.94 2.19 2.43 2.68 2.93 3.17 3.22 3.26 3.49 3.71 3.94 4.16 4.39 1.36 1.60 1.84 2.08 2.33 2.57 2.82 3.06 3.11 3.15 3.38 3.60 3.83 4.05 4.28 1.50 1.74 1.98 2.22 2.47 2.71 2.95 3.00 3.04 3.27 3.49 3.71 3.94 4.16 1.64 1.88 2.12 2.36 2.60 2.85 2.90 2.94 3.16 3.38 3.60 3.83 4.05 2.02 2.26 2.50 2.74 2.79 2.83 3.05 3.27 3.50 3.72 3.94 2.16 2.40 2.64 2.69 2.73 2.95 3.17 3.39 3.61 3.83 2.30 2.54 2.59 2.63 2.85 3.07 3.29 3.51 3.73 2.44 2.49 2.53 2.75 2.96 3.18 3.40 3.62 2.43 2.65 2.86 3.08 3.30 3.52 2.55 2.77 2.98 3.20 3.42 2.88 3.10 3.32 3.00 3.22

NOTE:

• Height differential not to exceed 4% of span (L/25) • Sag elevations are for use with cables donated as part of B2P’s recycled cable program

Volume 3: Suspended

Part 3 - Construction Guide



85

Cable Sag Setting There are many different ways to set the sag. Below, we will describe two of these. You can choose either way, as long as at the end of the process: • All walkway cables are aligned to one another • Both handrail cables are aligned to each other and are 1.1m higher than the walkway cables • The cable low point is at ‘f’ - low point elevation Tools Required • Cable hoist with cable winch • Abney level • Two long straight sticks (#1a, #1b) • 1 meter tall stick (#2) • T-level stick: see diagram • Spray paint

Step 1 Decide on Sag Setting and Cable Alignment Methods Depending on the availability of surveying tools, either an Abney level, a range finder, or an auto-level can be used for sag setting, and either a T-level-stick or a level can be used to insure cable alignment. If you choose to use T-level-stick, fabricate one using a 1.5 meter minimum length stick as the horizontal member, attach a second vertical stick at a perpendicular angle (use a square edge to confirm). Nail two angled supports for added rigidity and notch out 30mm guides on either end of the horizontal stick to allow the T-level stick to slide to the middle of the span without slipping off the cables. Place a plum bob at the center that hangs without touching the T-stick when the stick is completely vertical. Note: When using 3 walkway cables remember to leave space for the middle cable.

Sag set T-guide with plum bob suspended from center

Step 2 Mark Low Point f (lowest cable point) (if using Auto-level refer to volume 2: Feasibility and Topographic Survey)

Volume 3: Suspended

• • • •

Measure the low point ‘f’ (distance to lowest cable point) relative the low side tower For the handrail cables - measure ‘f’ from the top of the towers For the walkway cables - measure ‘f’ from the top of the walkway hump Mark clearly on the tower/tier with spray paint. This is your reference point for visualizing when the cable has reached the hoisting sag level • When ‘f’ does not lie on tower / tier structure, use 2 sticks and a range finder, auto-level or Abney level to find the lowest point.

Part 3 - Construction Guide



86

Step 3 Attach Cable Winch Connect the winch to the erection hooks and the first walkway cable to be tightened. This may require wrapping linked chain around the cable, or securing a piece of pipe with a clamp, to ensure no slippage. Important Safety Notice: Ensure that the winch you are using is correctly rated and in good working condition, and that the connection to the cable is secure.

Step 4 Zero Abney Level Lock the knob at zero degrees. Other possible tools – auto-level

Step 5 Raise Cable Raise the cable with the cable winch until the cable is well above the low point (‘f’) marked in Step 2 (lowest cable point). Look through Abney level towards cable in center of span to verify it’s above the marked point. Important Safety Notice: Make sure that only those working on the cables are in the near vicinity when tightening cable and that all participants are standing above the towers, anchors and cable, NOT below towers or cable.

Volume 3: Suspended

Part 3 - Construction Guide



87

Step 6 Hand-Tighten 2 Clamps Attach two (2) cable clamps to hold the cable and hand-tighten the clamps. Secure the tail (dead end) of the cable to another cable as an added safety precaution. If it slips too much, the other cable will catch it.

Step 7 Remove Cable Winch Detach the cable winch and set to the side.

Step 8 ‘Hit’ Live Cable 1. Loosen the clamps slowly a 1/4 turn. Using a large piece of wood, strike the cable just above the clamps. The cable should slip and lower very slightly with each hit. If the cable does not move at all, loosen the clamps slowly a 1/4 turn more until the cable moves when hit. 2. Look through the Abney level or auto-level from the lower sag point at the adjustable side toward the point marked in Step 2 on the other side. Make sure the Abney level is level by viewing the level bubble or that the auto level is set correctly. Lower the cable in this manner until the Abney level ‘sees’ the bottom point of the cable at the sag point marked in Step 2. When done, tighten/torque a minimum of two clamps to hold the cable in place.

Step 9 Repeat for all cables Repeat steps 6 to 8 for all cables

Volume 3: Suspended

Part 3 - Construction Guide



88

Step 10 Cable alignment With the T-level stick, or any other method you choose to use (in the picture using a level), make sure all walkway cables are aligned and level, and both handrail cables are aligned and level. If not, modify the cables as needed. (Easily done by adjusting the location of the clamp closest to the anchor.) Always slide the T- level stick or the level to the middle of the bridge and visually verify that the vertical stick of the ‘T’ is aligned with the plumb bob, or that the bubble on the level is in the middle.

Step 11 Add Clamps - Beam Anchor (for Drum Anchor please go to next page) Add clamps to all cables and tighten them per the information in 6.6: Cable Clamp Installation.

Red is Dead Never Saddle a Dead Horse

Volume 3: Suspended

Part 3 - Construction Guide



89

Step 11 Add Clamps - Drum Anchor (Rock conditions, for Beam Anchors see Previous Page) Set Sag and Temporarily Clamp Cables to Themselves Cable #1 wrapped around drum and attached back to Cable #1, likewise Cable #2 is attached back to Cable #2 as shown in figure #1 below. Use minimum of two (2) clamps and hand-tighten fully.

Attach Temporary Cable Piece Cut 5 meters of cable as temporary cable and place around the anchor. Attach the temporary cable to the ‘live end’ of both cables (#1 and #2) to keep the tension as shown in figure #2 below. Use minimum of two (2) clamps and hand-tighten fully. Remove Temporary Clamps Remove the hand-tightened clamps from cable #1 and move the loose cable tail to the opposing cable (#2) and clamp in place. Do the same for cable #2 as shown in figure # 3 below. Use the complete number of clamps required. Cables attached to themselves temporarily Remove Temporary Cable Remove the excess cable as shown in figure #4 below.





NOTE: The same apply both to the walkway cables on the inner drum, and the handrail cables on the outer drum. When using 3 walkway cables the middle cable stays attached to itself.

Volume 3: Suspended

Part 3 - Construction Guide



90

6.6 CABLE CLAMP INSTALLATION 6.6.1 CLAMPS TYPE, QUANTITY, AND TORQUE Proper cable clamp torquing (tightening the cable clamps sufficiently) is the single most important quality control issue for bridge construction. If the clamps are not tightened sufficiently, they may slip and fail causing the bridge to fall and risking lives. The required torque varies depending on the quality of the clamp and the clamp size. The table below is the Bridges to Prosperity standard for torque requirements for drop-forged cable clamps for a given cable and clamp diameters. Cable clamp manufacturers provide specifications that must be verified, as this chart is only given as a guideline.

Cable Diameter (inch) (mm) 5/8 16 3/4 19 7/8 22 1 25 1 1/8 29 1 1/4 32 1 3/8 35 1 1/2 38

Spacing (mm) 102 114 121 132 144 160 160 171

Drop-Forge clamps # of clamps Torque (foot-lbs) 3 95 4 130 4 225 5 225 6 225 7 360 7 360 8 360

DROP-FORGED CLAMPS ARE OF SUPERIOR QUALITY AND MUST BE USED ON ALL B2P PROJECTS.

Volume 3: Suspended

Part 3 - Construction Guide



91

6.6.2 CLAMP TORQUE & SPACING The torque required for drop-forged clamps will require a minimum 1 meter heavy open box wrench with pipe extension or socket wrench. A typical person is able to reach 100 foot-pounds of torque, so with a 1-meter extension he/she applies just over 300 foot-pounds of torque with their force applied at the very end of the wrench. If a 1 meter wrench is not available, use a breaker bar (cheater bar) with a socket wrench. If a torque wrench is available, read the amount of torque applied by tightening the nuts similar to a typical wrench. Read the side gauge and continue to tighten until specified torque is reached. Tighten until the diameter of the dead cable is reduced approximately 25% as shown to the right. Clamps must be placed such that the saddle is around the live or load-bearing cable and the pinched side is the loose or ‘dead’ cable as shown in the picture to the right. The cable clamps spacing (G) in the diagram below is also important and is detailed in the chart on the previous page.

Red is dead Never saddle a dead horse

Volume 3: Suspended

Part 3 - Construction Guide



92

6.7

CABLE CARE

Fill Tubes with Grout After completing the decking and making sure the bridge is aligned and no further adjustments are needed, fill the tubes with a wet cement mixture. This will reduce the potential for corrosion if water enters the underground tubes. A funnel created from a cut-off soda bottle is ideal for directing the watery grout into the tubes. The walkway tubes on the towers are easier to fill by poking a hole in the middle of the tube.

Volume 3: Suspended

Part 3 - Construction Guide



93

Roofing Tar on Cables that Lay Underground The cables which remain underground, and all the clamps, must be coated with a 5mm coat of roofing tar. This process seals the cable and reduces corrosion and cable weathering. Do this after completing the decking and making sure the bridge is aligned and no further adjustments are needed.

Loop Back Excess Cable To add redundancy in the case of potential cable clamp slippage, excess cable should be wrapped back into the approach area and clamped back onto itself. Care should be taken to clamp the dead end of the cable. (Note: In the picture to the left, the clamps were installed incorrectly.)

Volume 3: Suspended

Part 3 - Construction Guide



94

QUALITY CONTROL CHECKLIST: SETTING SAG AND CABLE CARE Initial to confirm that each step has been completed Step Reference/Guide

Mason/CM

Tech. Supervisor

----------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------- ------------------

Setting Sag Before Step 1

Anchor was cured for 7 days or TAB approved alternative cure procedure

Step 1

Design sag (Bd) was calculated as span (L) x 5% = __________

Step 1

Hoisting sag (Bh) calculated as span (L) x 4.6% = __________

Step 2 Step 11

Distance to low point of cables set: f = ___________ (relative to low side) calculated using Bh

Step 12

Verify number of clamps used per cable per side: ________ and spacing between clamps : ________

Step 12 Step 12

Clamps tightened to 25% reduction?

Cable Care

All cables are set level and do not cross each other?

Specified number of cable clamps and specified clamp spacing used? ----------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------- ------------------

Section 6.7

Care has been taken to insure no kinks or excessive broken threads on cable?

Section 6.7

Tubes have been filled with grout, avoiding air bubbles?

Section 6.7

Buried cables have been covered in 5 mm roofing tar?

Section 6.7

Excess cable has been attached back onto itself?

As-Build

----------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------- -----------------As-built measurements were taken for this section QC photos taken

Safety

----------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------- -----------------All near misses and incidents documented

Name of Mason/Construction Manager : Name of Tech. Supervisor:

Volume 3: Suspended

Part 3 - Construction Guide



95

6.8 BRIDGE APPROACH CONSTRUCTION Tools Required • String • Shovels

• Plumb bob • Buckets

Materials Required • Cement • Sand • Tamper • Broken stone • Gravel

Step 1 Build Approach Walls Set a plumb line between the edge of the top tier and the front of the anchor excavation. Dig a 25cm deep and minimum 40cm wide trench to lay the first layer of the wall. If using locally available stone, start with the largest stones on the bottom layers. Build the masonry walls no higher than 1.00m before backfilling. If the wall height exceeds 2 meters (for 3 tier structure) build the wall stepped on the outside. Build 70cm wide wall for the first meter, 50cm wide wall the second meter, and 30cm wide wall the third meter. CMUs should be used only if there is no other option, and should be double layered and are not recommended for walls over 2m high.

Step 2 Backfill Area Fill the area with available stone, gravel and sand ensuring the stone is vibrated and tamped into place. Note: Soil is not to be used as a backfill material. Ensure regular compaction with a tamper to reduce settlement. No soil or organics should be used as they will cause settlement. If there is soil in-situ (undisturbed soil between the approach ramp walls), it can remain, but no other soil is permitted.

Step 3 Concrete Slab The final layer of the approach must be a layer of compacted gravel, 10cm thick. Take care to compact by using either animals or people jumping on the area. Following compaction, cover the approach with a concrete slab, 10cm thick. If left rough, the slab will provide more traction.

Volume 3: Suspended

Part 3 - Construction Guide



96

6.9 WOOD DECK INSTALLATION While placing the deck boards, everyone on the bridge must wear fall protection. Tools Required • Hammers • Wood saw • Wrenches • Hack saw and blades • 2cm diameter pipe (for bending suspenders) Materials Required • Crossbeams • Deck boards • Nailer boards (if needed) • Galvanized screws: long enough to hold the wood-width used • Steel deformed rebar: (2 x (Span + 1)) pieces, 10mm (#3) Ø , cut to 1.80 meters

Crossbeams

There are three types of crossbeam alternatives: 1) wooden crossbeam with a nailer, 2) wood crossbeam without a nailer, and 3) steel crossbeam with a nailer. The nailer is the same width as the decking panels, and is attached to the top of the narrower cross-beam to increase the amount of surface area available for nailing the decking panels. The nailer improves constructability and allows for a smaller crossbeam size. Steel crossbeams can increase the lifespan of crossbeams, but will have to be sized by an engineer. B2P does not currently have a standard for this for suspended bridges.

Wood crossbeam with a nailer (recommended)

Volume 3: Suspended

Wood crossbeam without a nailer

Part 3 - Construction Guide



97

Step 1 Decking Preparation Crossbeam preparation Cut (span plus 1) crossbeams to 136cm minimum length and pre-drill for suspender connections. The hole spacing is based on the number of walkway cables. See Volume 3, Part 2: Suspended Bridge Construction Drawings. The hole size should be bigger than the suspender size (for example - if a 10mm bar is used, drill a 13mm hole). Deck preparation Cut decking panels to 3.0 meters for any span over 60 meters and preferably all spans. If the bridge is shorter than 60 meter span, 2.0 meter decking panels are allowable. The total number of decking panels is equal to [span divided by length of each board (either 2.0 or 3.0)] multiplied by five (5), as there will be five decking panels across, each 20cm wide. If ‘nailers’ are used, an additional (span plus 1) meters of decking boards will be required, cut at 1.0 meter lengths.

Step 2 Suspender Preparation Cut minimum 10mm (#3) diameter deformed rebar into 1.8 meter long pieces. Using deformed rebar is recommended as smooth rebar tends to be of lower quality. The total number of suspenders required is equal to 2x(span + 1). For example, a 30 meter bridge would require 62 suspenders. Bend the suspenders as specified in the relevant drawing for your design in Volume 3, Part 2: Suspended Bridge Construction Drawings and paint with anticorrosive paint.

Volume 3: Suspended

Part 3 - Construction Guide



98

Step 3 Attach Nailers to Crossbeams (Nailer Recommended) If using nailers, cut (bridge span plus 1) boards to 1.0 meter lengths. Attach the nailer to the crossbeams with a minimum four (4) galvanized screws, aligning along the center of each board. The crossbeam should exceed the length of the nailer by at least 36cm, 18cm on each side.

Step 4 Install Crossbeams The first crossbeam must be firmly attached to the walkway hump so that the decking does not slip during installation. Insert the suspender and wrap around the crossbeam and handrail cable. Use a temporary clamp on the walkway cable to hold the first crossbeam in place flush against the front of the tower. The next two (2) crossbeams are then attached to the walkway cable by inserting the suspenders through the bottom of the crossbeam and around the walkway cable. The top of the suspender is bent over the handrail cable, but not fully wrapped yet.

Step 5 Start Decking Cut one deck panel to allow for deck panel staggering. If using 2.0 meter panels, cut starter pieces into two (2) 1.0 meter panels. If using 3.0 meter panels, cut into one (1) 1.0 meter panel and one (1) 2.0 meter panel. Push the second crossbeam 1.0 meters away from the secured first crossbeam. Push the third crossbeam 1.0 meter further so each are at a 1.0 meter spacing on center. Begin with 3 (3) full-length deck panels and two (2) partial decking panels. Start with a full length panel on one side, second panel a shorter piece, third or middle panel full length, and so on. Place all decking ‘“heart down” to minimize cupping, as shown below. Correct

Volume 3: Suspended

Part 3 - Construction Guide

Not Correct



99

Step 6 Screw Deck Panels Using 10cm galvanized screws, attach the end of each panel to the middle of the first and last crossbeams (or nailer) it lays on using 2 screws. Make sure there is enough room to connect the next deck panel. Place another screw connecting the panel to the middle crossbeam. It may be necessary to pre-drill screw holes in the decking based on the hardness of the wood and the quality of the drills used for the screws. This can be decided on-site based on the quality of materials and tools available.

Step 7 Lay Decking and Wrap Suspenders Continue until the bridge is complete, adding only three (3) or four (4) crossbeams and suspenders at a time. When all decking is done, go back and wrap the suspenders around the handrail.

Volume 3: Suspended

Part 3 - Construction Guide



100

6.10 CONNECTING DECK TO APPROACH

Walkway Tower Tube detail

Tools Required • Hammers • Wood saw • Wrenches • Hack saw and blades • 2cm diameter pipe (for bending suspenders) Materials Required • Deck panels



• 1 bag cement

The ends of the decking panels end at an elevation above the ‘“hump” of the tower crest as shown in the top right picture. There are several design alternatives to mitigate this potential safety hazard. To ensure a smooth transition between the decking and the ramp approach, additional formwork was required during tower construction. Each walkway cable was threaded with tubing, and each cable is aligned between saddles. An additional layer of concrete was formed over the tubes to an elevation equal to the total depth of the decking. This allows for a flush junction, but requires precision in concrete works. Reference top drawing to the right for details. At the insertion point where the cable enters the approach, a small formed lift will hinder the ability for water to pool at the connection. A small wedge may be formed with finishing concrete.

Volume 3: Suspended

Part 3 - Construction Guide



101

6.11 FENCING INSTALLATION Tools Required • Wire cutters • Pliers Materials Required • Galvanized fencing mesh (recommended 1.2 meters high) • U-nails • Galvanized tie wire

Step 1 Unroll Fencing and Connect Rolls Uncoil the fence onto the ground (or the bridge) and stretch the wire out as much as possible. Several rolls may need to be used depending on the length of the bridge. Connect one roll to the other by placing the 2 ends adjacent to one another (making sure both ends facing the same direction) and weaving an opposite direction wire in between. The same method is applied to “cut” the excess length.

Step 2 Pull the Fence Tightly and Connect to Deck and Suspenders Lift the fence up. In small sections, pull it tight and connect the bottom of the fencing to the decking panels near the walkway cables with u-nails or regular nails bent over the edge. Attach the fencing to each suspender with galvanized tie-wire.

Step 3 Attach to Handrail Cable After the fence is placed throughout the span of the bridge, push the top of the fencing over the handrail cables and tie tightly against itself with galvanized tie-wire. If the fence height exceeds 1.5m, the excess fencing should wrap over the top cable or under the decking at the base.

Volume 3: Suspended

Part 3 - Construction Guide



102

QUALITY CONTROL CHECKLIST: BRIDGE COMPLETION Initial to confirm that each step has been completed Step Reference/Guide

Mason/ Construction Manager ----------------------------------------------------------------------------------------------------------------------------------------------------------

Approach Step 2

Approach filled with Rock (not soil)?

Step 2

Was the approach filled in lifts of 50cm with tamper?

Step 3

Was the approach finished with a 10cm concrete slab? ----------------------------------------------------------------------------------------------------------------------------------------------------------

Decking During Step 1

Holes oversized for suspender rebar?

Before Step 4

Was a termination between approach and deck created?

Step 7 Steps 1-3 in Fencing Installation

As Built

Tech. Supervisor

--------------

-------------

--------------

-------------

--------------

-------------

--------------

-------------

Suspenders wrapped tightly around handrail cables? Fencing tied tightly and frequently to avoid gaps? ---------------------------------------------------------------------------------------------------------------------------------------------------------As-built measurements were taken for this section QC photos taken

Safety

---------------------------------------------------------------------------------------------------------------------------------------------------------Fall protection used above 6ft Harness + lanyards have been inspected Fall Rescue plan completed All near misses and incidents documented

Name of Mason/Construction Manager : Volume 3: Suspended

Part 3 - Construction Guide



103

SECTION 7: BRIDGE COMPLETION The Bridge Registration includes both a technical As-Built assessment of the bridge as well as a socioeconomic survey evaluating the impact of the bridge on the local community. The agency responsible for the construction of a bridge needs to keep records of this information for all completed bridge projects. Bridges to Prosperity also asks to receive a copy. By keeping record of completed projects, this ensures any follow-up quality control inspections and third party monitoring are able to fully understand the structure as it was built before starting the assessment, and furthermore helps quantify the impact of the bridge on the community. As such, the submittal of the Bridge Registry to B2P is required for all co-sponsored bridges, and appreciated for all others. Please contact B2P at [email protected] for any clarification or submittals. All referenced forms are included in Section 5 of this manual.

7.1

BRIDGE PORTAL Bridge documentation must be submitted to B2P following the completion of the bridge in order for the project to be certified as a Silver, Gold or Platinum B2P Bridge. The purpose of the registration is to create institutional memory surrounding a project and to offer additional support for the inspection, maintenance, and impact evaluation of the projects using B2P’s standards. The B2P Bridge Portal is a database of bridge information that will be able to be accessed by a select number of individuals and organizations in the 2014-2015 year and will be released for full use following. Please contact [email protected] for further information.

7.2 SOCIOECONOMIC IMPACT

Pedestrian bridges have varying impacts on differing communities. Most typically, economic stimulus is evident from the increased access and drastic improvements in public health and education are seen as well. To better understand the impact that bridges have on your specific community, it is essential to complete a socioeconomic survey both before the bridge is constructed, and again following the completion. It is ideal to complete the survey several times throughout the lifespan of the bridge, as the impact of the bridge may not be immediately evident. The survey details traffic information, general demographic and economic information of the community members. If additional information is of relevant to the specific community, please include it. **Please fill out and return the Bridge Registration Form and Socioeconomic Implication forms to Bridges to Prosperity (contact at [email protected]). These forms can be found in Volume 2.

Volume 3: Suspended

Part 3 - Construction Guide



104

BRIDGE BUILDER MANUAL 2014

VOLUME 3.4

SUSPENDED CABLE BRIDGE M A I N T E N A N C E & E VA L UAT I O N FOURTH EDITION

Volume 3: Suspended

Part 4 Maintenance & Evaluation

2014

1

Introduction NOTE: a copy of this section of the manual should be left with each partnering community and a second copy with the sponsoring institution upon the completion of a bridge project. Maintenance is essential for the safety of all bridge projects. As should be outlined in project agreements, the community, local government, and bridge committee leaders are responsible for monitoring the bridge to ensure safety and for performing basic annual maintenance. B2P technical inspection requirements are not covered herein, but please contact us for further information as required. Bridge maintenance includes both annual bridge upkeep and scheduled inspections, typically required twice in the first five years of bridge inauguration. The community is responsible for general bridge upkeep and the local sponsoring institution (typically the government body) is responsible for returning to the site for technical inspections. The Bridge Committee (reference Volume 1) must designate a person or team of people to inspect the structure after every rainy season from the community and the sponsoring institution shall designate the engineer to complete inspections. If Bridges to Prosperity is directly involved in the construction of the bridge or certifies a structure as a Gold or Platinum project, B2P will work with the agency to designate responsibility and support when required. For concerns of safety concern or impending bridge failure, contact Bridges to Prosperity immediately (contact at [email protected]), irrespective of our involvement.

Volume 3: Suspended

Part 4 Maintenance & Evaluation

2

VOLUME 3 SUSPENDED PEDESTRIAN BRIDGE Part 4: Maintenance Table of Contents Section 1: Committee Annual Inspection 1.1 Inspection Checklist Section 2: Technical Inspection 2.1 Materials Required

2.2 2.3

Technical Inspection Considerations Technical Inspection Form

Section 3: Maintenance 3.1 Overall Site Condition

3.2 Foundation Tiers & Towers 3.3 Anchors 3.4 Cable & Clamps 3.5 Approach 3.6 Decking



Volume 3: Suspended

Part 4 Maintenance & Evaluation

3

SECTION 1: BRIDGE COMMITTEE ANNUAL INSPECTION In order to keep the bridge in optimum condition, continual upkeep is required. An annual inspection is essential to maintenance. Following the end of the rainy season, one or more representatives of the Bridge Committee must visit the bridge site and complete the inspection outlined below. Once the inspection is complete, corresponding maintenance must be arranged and carried out (see Section 3).

1.1

Annual Inspection Checklist • Remove any excess mud and debris from the bridge deck. • • • • • • •

Ensure weeds and plants growing beneath the bridge do not obstruct the bridge. Ensure all bolts, screws and nails are in place and tightened. Replace deteriorating wood deck panels. Replace deteriorating crossbeams. Ensure that fencing is secure. Should any wires be loose or fencing missing, repair or replace to original condition. Check for erosion. Should erosion or scour occur, causing the water to reroute toward the anchor or approach, contact the local supporting agency and request assistance with a drainage structure. Measure the distance between the paint on the cable and the saddle guides (inset bottom right). If the cable has shifted more than ten centimeters (0.1m), contact the local supporting agency immediately and if possible, Bridges to Prosperity (contact at www.BridgestoProsperity.org).



Saddles

Paint Line

Volume 3: Suspended

Part 4 Maintenance & Evaluation

4

SECTION 2: TECHNICAL INSPECTION Following the completion of the bridge, a follow-up technical inspection must be completed a minimum of two times during the first five years of the bridge service life. If the pedestrian bridge continues to be used beyond 10 years, a technical inspection should be completed every five (5) years. Beyond 30 years, the bridge must be reviewed by an engineer to ensure safety of cables, structure and decking. Upon completion, please keep one copy of the completed report and send a copy to Bridges to Prosperity.

2.1

Materials Required • 50 meter measuring tape • Digital Camera • Torque Wrench • Socket (sized to correspond to cable diameter) • Pen & paper • Copy of Technical Inspection Form

Volume 3: Suspended

Part 4 Maintenance & Evaluation

5

2.2 Technical Inspection Considerations General Bridge Data All relevant information regarding the location, construction completion date and previous inspection date is available from Bridges to Prosperity. It is best to have all of this information on hand, including a copy of the original bridge drawings, before heading into the field. This will allow the inspector to note any significant changes in sag, span length, or easily identify repairs that have been performed since the last Technical Inspection was carried out.

Cable Condition Inspect the cable at all points of insertion into concrete, the approach or into the ground. Look for frayed, stretched, or worn cable along its entire length. Reference the colored mark on the cable, which originated between the guides on the saddles. If the amount of movement exceeds 1% of original cable length, cable slip or excessive cable stretch has occurred (if length unknown, warning at more than ten centimeters (0.1m)), please contact B2P immediately ([email protected]).

Cable Clamps Inspect all clamps that are visible above ground. Using a torque wrench, document existing torque on each aboveground clamp. For torque standards, first measure the diameter of the cable and reference the corresponding minimum torque from the torque requirements on the following page. If the measured torque is less than 80% torque required, re-tighten all above-ground clamps to specified torque. If actual is less than 60% of specified required torque, notify implementing agency immediately to discuss need to rip out approach or return to add additional clamps. If a torque wrench is not available, the inspection should check to make sure the nuts are tight using a minimum 3-foot long wrench. If the nuts can be easily turned, they should be re-tightened. Discuss the issue with the community to ensure that no one is loosening the nuts.

Decking A survey noting condition of the decking along the span length must be completed. Missing planks or crossbeams, recent repairs, type of crossbeam, fastener type(s), suspender size, suspender material (smooth or ribbed rebar), fencing material, etc. will all be noted. Inspection of the deck will require access to the underside of the bridge. As such, it is best to arrange for inspections to be completed in the dry season.

Volume 3: Suspended

Part 4 Maintenance & Evaluation

6

Approach Walls & Ramp Inspect the condition of the approach walls and ramp. Evaluate and document extent of cracking on concrete approach ramp. Typical source of crack propagation is the insertion point of cable, or settlement within the approach. Note opinion on source of cracks. If cracks between rock walls exist, look into the approach to evaluate if excessive settlement has occurred inside. Note if any usage issues occur. This may include water pooling, excessive cracks or bumps in the approach or connection to ground, etc.

Anchors Inspect the area surrounding the anchors (far back side of approach, on both abutments). Take special note if erosion has occurred and what the drainage path of run-off water appears to take. If the erosion has caused scour, undercutting the anchor, reference the maintenance section. Walk behind the approach, if possible. Note if the cable is kinked at the saddles, implying the cable is not wrapped directly behind the corresponding cable saddle. For rock conditions, the anchor is a cylindrical drum. The cables also should come straight off the saddles. Note if the cable is kinked.

River Bank Erosion and Site Evaluation Inspect the area surrounding the bridge, on both abutments. Take special note if erosion has occurred and what the drainage path of run-off water appears to take. If the erosion has caused scour, undercutting the anchor, approach or foundation structure, reference the maintenance section.

Foundation Tiers & Towers Inspect the foundation tiers and towers. Note the masonry condition of towers. Is one able to pick out aggregate with hands? On either side, verify the base foundation layer is level. Note if the foundation structure appears to be dipping towards the water or slipping, or if the walls appear to be rotating under the ramp or the approach. If the structure has settled in either manner creating change of elevation of line greater than 30cm, contact agency responsible for bridge.

2.3

Technical Inpsection Form At the time of print, the B2P Inspection protocal is going under significant updates. As such, the Techincal Inspection Form is not included herein but can be requested via [email protected].

Volume 3: Suspended

Part 4 Maintenance & Evaluation

7

Section 3: Maintenance This section includes mandatory upkeep items to be completed during every annual inspection, as well as solutions to repair bridge components should maintenance be warranted. The Maintenance Section includes the following sections:

3.1

3.1 3.2 3.3 3.4 3.5 3.6



Overall Site Condition Cables & Clamps Decking Approach Walls & Ramp Anchors Foundation Tiers & Towers

Overall Site Condition If either the annual community or Technical Inspection shows erosion and scour are undermining the bridge structure, a drainage structure may allow the water to reroute, thus saving the structure from further damage. Slope protection and drainage systems are required at sites when excess run-off may influence the slope stability. It is recommended to avoid sites where any instability is prevalent. If unavoidable, it is necessary to drain out the runoff and seepage to ensure the stability of the slope and to avoid under-scour of structures. Water should be collected as closely as possible to its origin and navigated away from the bridge structures. This may require a surface catch drain on a slope, drainage around the structure or both. Examples of subsurface and surface drainage systems are shown below. For further details, reference Volume 2.

Subsurface Drainage

Surface Drainage

Volume 3: Suspended

Part 4 Maintenance & Evaluation

8

3.2

Cables & Clamps If the cable is found to be corroding or fraying, estimate the percentage of the cable cross-section that has been damaged. If greater than 10% of the cable diameter is fraying, evaluate the extent of the damage. If localized in one point, consider a splice. Reference cable-manufacturing materials for details. If the clamps are found to have less than 80% of required torque, each above-ground clamp must be re-tightened. The picture to the top right depicts the cross-sectional reduction that is required when the clamps are fully torqued (assuming drop-forged, not malleable. For more information, see Volume 3, Part 3). Bottom right shows the proper length of the breaker bar or torque wrench required to apply the adequate amount of torque. If nuts are to be re-tightened, “ping the threads” using a hammer and flatnosed screw driver to flatten the threads will ensure future loosening does not occur. If the clamps are found to have less than 60% of the required torque, additional clamps must be added. In severe cases the approach should be removed to tighten clamps below ground.

3.3 Decking If any decking panels are rotting through or missing entirely, they must be replaced. The standard thickness of a decking board is 5 cm, but verify with those on site before purchasing. Reference Volume 3, Part 2 Drawings, specifically the decking drawings for complete details. Note that the pattern of laying the deck panels requires a stagger, as shown in the picture to the right. If any crossbeams are in need of replacement, either an additional board must be attached to the bottom as reinforcement or the beam must be replaced. Crossbeams should be replaced one at a time. Trying to replace multiple beams at one time may result in the distance between the handrail and the deck cables being compromised. If replacement is chosen, start by removing the deck panels directly above the crossbeam in question. Unwrap the fencing in the direct location; cutting may be required. Secondly, unwrap the suspenders from the top of the cable, which likely will require a pipe. Unwrap the suspender from the crossbeam. Take new pre-drilled crossbeam and suspender and fit into place. Reference Volume 3, Part 3 Construction for details. Complete the process by screwing and nailing the deck boards back into place. Replace and repair any damaged fencing before documenting the completed maintenance project.

Volume 3: Suspended

Part 4 Maintenance & Evaluation

9

3.4

Approach Walls & Ramp If the quality control inspection finds that the approach structure is degrading, use a cement mortar to patch the areas. If severe degradation, consider patching with wedge stones. If the ramp is cracking from settlement (not just localized cracking around the insertion points of the cable), rip out the 5cm thick concrete ramp topping, backfill the approach with additional well-graded large aggregate and stone and recover with a fresh layer of concrete, 5cm thick.

3.5 Anchors If the Quality Control Inspection notes that erosion and scour are undermining the anchor, a drainage structure may allow the water to reroute, thus saving the structure from further damage. Reference Volume 2 for further details on drainage structures.

3.6

Foundation Tiers & Towers If the quality control inspection finds that the masonry structure is degrading, use a cement mortar to patch the areas. If severe degradation, consider replacing when possible. If the structure is found to be slipping (either slipping downhill, or tipping forward), consult a local engineer to evaluate the stability of the slope. If considered unsafe, close the bridge. It is possible to reconstruct the structure of the failing side using many of the scrapped materials, but do not relocate at such a distance that the cables create a lateral load on the opposing side towers. A local engineer may recommend butressing the area with a column or adding a ring of support around the tier if it is leaning or severely degraded.

Volume 3: Suspended

Part 4 Maintenance & Evaluation

10